One year Into Trump's presidency, agencies work to make good on his campaign promises

— -- The first 12 months of President Donald Trump's administration showed little regard for precedent, tradition or protocol.

As he set about putting top officials in place at the federal agencies charged with carrying out his administration's priorities, the former businessman turned politician chose men and women whose decisions shook up both national politics and upended the traditional ways policies are executed.

Meanwhile, a nuclear North Korea, a depleted ISIS footprint, investigations into possible Russian election meddling, congressional efforts to repeal Obamacare and the passage of a $1.5 trillion rewrite of the U.S. tax code dominated front pages, cable news and Twitter feeds across the country.

Those headlines, just to name a few, came at such a fast and furious pace that it was easy to miss stories with wonky headlines--but significant impact on policy- and on millions of American lives.

They were important as well because they described Trump's mission to establish America as an economic and military force-- often by dismantling Obama-era policies. And nowhere was that more apparent than inside the federal agencies carrying out the will of the White House.

The administration took historic steps to boost American energy production, redefine the term "employer," altered the standard of proof in sexual assault investigations in schools and weathered multiple devastating hurricanes and fires.

ABC News has broken down some of the most important changes from the federal agencies during the Trump administration's first year in Washington:

Census Bureau

Leader of agency: Acting Director Ron Jarmin

What happened: The Census Bureau is facing steep challenges to pull off an accurate and trustworthy census in April 2020, so Commerce Secretary Wilbur Ross, a former census taker himself, has overseen a changing of the guard. Former Director John Thompson is out and interim Director Ron Jarmin has stepped in to lead an office under major pressure to keep costs down during a digital transformation. The 2010 U.S. Census cost $12.3 billion, the most in the survey's 220-year history. The agency has abandoned two of three scheduled trial runs. Critics are concerned political considerations are affecting a normally rigidly nonpartisan agency that now faces the task of tallying immigrants who fear newly-aggressive immigration enforcement.

Why you should care: Many experts are concerned the accuracy of the once-a-decade tally is at risk, calling into question a pillar institution of the United States. A disputed tally of national demographics could have profound repercussions in a nation already struggling to agree on the most basic facts. Commerce Secretary Ross says he is "keenly aware" of the challenges, but is "confident in our ability to conduct a full, fair and accurate 2020 census." The nonpartisan agency's census is the basis for redrawing of congressional and state legislative districts, critical to the distribution of more than $500 billion in grants and subsidies to local governments and serves as a benchmark for businesses, governments and researchers. Lawsuits and public disputes over a national census could drain public trust in a core government function.

Central Intelligence Agency

Leader of agency: Director Mike Pompeo

What has changed: CIA Director Pompeo has called for the agency to aggressively step-up its overseas covert operations. The CIA created a Korea Mission Center and Iran Mission Center to exclusively focus on the security threats posed by each country. More than other recent CIA Directors, Pompeo has frequent and direct access to President Trump-- who has requested Pompeo personally deliver his daily intelligence brief. Critics say Pompeo has politicized some of his agency’s intelligence products. Pompeo has labeled WikiLeaks “a hostile intelligence agency” --a shift for the former Republican congressman who during the 2016 election applauded its disclosure of internal Democratic Party emails.

Why you should care: Pompeo is respected internally at the CIA for his grasp of world affairs and for favoring a more aggressive pace of covert operations. But there has been criticism that Pompeo is not as apolitical as his predecessors and is not shy about weighing in on policy matters unrelated to intelligence. Pompeo also works for a president critical of the U.S. intelligence community, particularly the assessment that Russia interfered in the 2016 presidential election. Pompeo has downplayed the significance that Russian interference may have had on the election. As a key Trump advisor, Pompeo has been rumored to be possibly moving to the State Department to succeed Rex Tillerson.

Customs and Border Protection

Leader of agency: Acting Commissioner Kevin K. McAleenan

What has changed: In fiscal year 2017, CBP recorded the lowest level of illegal cross border migration on record - measured by the number of arrests by U.S. Border Patrol and people found inadmissible to the U.S. at ports of entry. April had the lowest month of border enforcement activity on record. However, since May, there has been an uptick in illegal crossings, especially by unaccompanied children and families.

CBP said that this decline reflects the administration’s commitment to the rule of law. In January, President Trump signed an executive order directing CBP to immediately begin the process of hiring 500 additional Border Patrol agents. The agency said that 2017 was a “ramp-up year” in order to implement the capability to hire the agents that Trump has requested and that it is “well-positioned” to hire the 5000 agents next year.

CBP is also managing one of the administration’s most controversial and ambitious proposals - the southwest border wall prototypes, which were built in San Diego for testing late this year. The prototypes are the first steps in CBP’s efforts to build a wall, although administration officials have acknowledged that a future wall is unlikely to stretch from sea to shining sea, despite Trump's promise to cover the entire border. The cost and timing of the wall remain in limbo.

Why you should care: CBP’s hiring efforts and push to build a wall along the southwest border will have a lasting impact on the ability to the U.S. to continue to stem the flow of illegal immigration and fight against the tsunami of illicit drugs entering the country.

Department of Agriculture

Leader of agency: Secretary Sonny Perdue

What has changed: One of the most noticeable changes the USDA made this year was its decision to roll back healthy school lunch rules put in place under the Obama administration-- part of Michelle Obama's push for kids to eat healthier foods. Perdue decided to reverse that policy and allow foods like chocolate milk back into school lunches, give schools an exception to a rule that required they provide only whole grain bread, and will postpone requirements that lunches have less sodium, saying that the Obama administration rules were too expensive and hard for schools to enforce. Perdue has also been working to renegotiate trade deals to export U.S. products to Asian countries and the European Union, and has said he will work with President Trump to renegotiate the North American Free Trade Agreement to benefit American farmers.

Why you should care: The Obama administration proposed rules about healthy school lunches to help reduce rates of childhood obesity by helping kids choose healthier foods. USDA programs to support farmers and negotiate international trade deals can also affect the price of groceries. More than half of the USDA's budget goes to programs such as food stamps and those same programs were used to provide food and financial help to people who lost their homes or crops after natural disasters like Hurricane Harvey.

Department of Commerce

Leader of agency: Secretary Wilbur Ross

What happened: In 2017, the U.S. gross domestic product, or GDP -- a broad measurement of Americans’ spending on goods and services-- grew at its fastest pace in three years, increasing by more than three percent for the second and third quarters of 2017. While the rate is likely inflated by goods yet to be sold-- a factor that accounts for nearly a quarter of GDP growth -- Americans have not seen a GDP increase like this since 2014, when GDP hit 5.2 percent under President Barack Obama.

Why you should care: While some remain skeptical the economic boost will survive long term, for President Trump 2017 closed on a high note of GDP reports. A stronger annual GDP -- a campaign promise from the president -- remains to be seen, but his recent victory on tax cuts is part of the president’s plan to get there.

Department of Defense

Leader of agency: Secretary James Mattis

What has changed: President Trump delegated to the military additional authorities in the fight against terrorist groups in Syria, Iraq, Afghanistan, Somalia, and Yemen. Three thousand additional U.S. troops are part of the administration’s new strategy in Afghanistan that hopes to change the momentum after 16 years of war there. In August, Trump directed the Pentagon to ban transgender individuals from serving in the military – reversing an Obama-era decision that allowed those individuals to serve openly.

Why you should care: The U.S. military conducted airstrikes in six different countries during President Trump's first year in office-- despite his promises to avoid getting the U.S. more involved in overseas conflicts. In addition to more troops in Afghanistan, there are more American boots on the ground in Somalia and Syria as well. The war against ISIS made significant strides as the group lost virtually all of the territory it once controlled in Iraq and Syria. But even once the terror group is defeated, the Pentagon acknowledges American troops will need to remain to stabilize those countries and prevent ISIS from re-emerging as a threat. Complying with a court order, the Pentagon said it would allow transgender individuals to join the military as of Jan. 1, but it's still unclear how that will occur or what will eventually happen to the transgender individuals currently serving. Trump's new policy that calls for them to be discharged was supposed to go into effect in March.

Department of Education

Leader of agency: Secretary Betsy DeVos

What happened: Following a confirmation battle, Secretary Betsy DeVos has taken steps to roll back several policies implemented by the Obama administration. In February, the department withdrew Obama-era guidance directing schools to allow transgender students to use bathrooms that match their gender identity. Then, in September, following a controversial meeting with so-called men's rights groups, the department rescinded another Obama-era edict requiring schools use the lowest standard of proof in sexual assault investigations.

Why you should care: This year, public schools enrolled more than 50 million children, employed more than three million teachers, and planned to spend around $624 billion, according to the National Center for Education Statistics. Colleges enrolled an additional 20 million students, who spent, on average, more than $22,000 on tuition, fees, plus room and board. Though education is primarily a state and local government responsibility, the federal officials identify best practices, distribute federal financial aid, and enforce anti-discrimination laws.

Department of Energy

Leader of agency: Secretary Rick Perry

What happened: Secretary Rick Perry says he regrets ever saying the department he now runs should be eliminated, but he seems determined to run it according to the president's agenda. This month,, the Federal Energy Regulatory Commission rejected Perry's proposal to subsidize coal-fired power plants, a move that would shift policy towards fulfilling the president's campaign promise to prop up the coal industry, but likely at the expense of bill-payers. In addition to policy moves, the Energy Department continues to oversee the rebuilding of Puerto Rico's electrical grid by appointing a deputy secretary to monitor progress. A senior official in the Army Corps of Engineers said DOE was "overwhelmed" by the devastation.

Why you should care: Perry's proposal to subsidize coal-fired power plants should not surprise anyone, but the reasons behind it are turning heads. The former Texas governor says the move would make the electrical grid more reliable, as coal plants can store a 90-day supply of fuel off site, citing emergencies such as the 2014 polar vortex that brought frigid winds to the Northeast. What Perry seemed to forget is that some coal-fired plants were unable to generate electricity because coal piles and equipment froze. It's unclear if this move would make progress in securing the grid, but it would support the president's goal of reviving the nation's dwindling coal business and satisfy industry leaders who have been jockeying for the Energy secretary's ear since soon after the inauguration.

Department of Health and Human Services

Leader of agency: Acting Secretary, Eric Hargan; Nominee, Alex Azar (awaiting Senate confirmation)

What has changed: In February, former Congressman Tom Price began his tenure as Secretary of Health and Human Services. During his confirmation hearing, Price made headlines for his position on the Affordable Care Act -- but soon, Price was in the headlines himself when Politico reportedhe spent over $1 million as HHS Secretary for private jet travel. Price resigned in September. The change in leadership overshadowed significant changes to HHS health care policy and the Affordable Care Act. One of the most controversial changes allowed employers to opt out of paying for employee contraception. HHS this year also slashed advertising dollars for Obamacare, cut the Open Enrollment period for Obamacare in half, and supported the Trump administration’s decision to end cost-sharing reduction payments to insurance companies, creating uncertainty in the insurance marketplaces.

Why You Should Care: In the first year of the Trump administration, HHS did a 180-degree pivot on the Affordable Care Act, sparking uncertainty in the individual marketplaces, and causing premiums to spike. As the health care industry is still getting settled into the Affordable Care Act, critics say the Trump administration is slowly chipping away at its foundation at HHS. Congress failed to repeal and replace Obamacare, but the Department of Health and Human Services weakened the law in Trump's first year by slashing funding, ending discounts to middle-income and low-income consumers and allowing employers to deny contraception coverage. The individual mandate was repealed as part of tax reform in late 2017.

Department of Homeland Security

Leader of agency: Secretary Kirstjen M. Nielsen

What has changed: Over the past year, the department has been at the forefront of Trump’s major executive policy decisions, including the travel bans, enhanced immigration enforcement and border security. Since Trump took office, the department has had two confirmed secretaries and one acting secretary. Retired Gen. John Kelly served as DHS secretary from Jan. 25 until the end of July, when he went to the White House, replacing Reince Priebus as the president’s chief-of-staff. Nielsen – Kelly’s chief of staff at DHS – was picked to succeed her former boss. She was sworn in on Dec 6, 2017.

Why you should care: DHS has a wide-ranging mission that covers everything from counterterrorism and cyber security to enforcement of immigration laws and response to natural disasters. Under the current administration the department has overseen the development of southern border wall prototypes, a surge in immigration-related arrests, the end of the Deferred Action for Childhood Arrivals (DACA) program, the end of Temporary Protected Status (TPS) for citizens of five countries, as well as the federal response to Hurricanes Harvey, Irma, Maria and other natural disasters. The department also reminded Americans to remain vigilant against potential terrorism, with increasing concern about tactics like vehicle ramming attacks, end-to-end encryption use, and a warning that homegrown terrorists may carry out violence in the U.S. instead of attempting to travel overseas to fight.

Department of Housing and Urban Development

Leader of agency: Secretary Ben Carson

What happened: Secretary Carson, whose nomination faced controversy due to his lack of experience in housing policy, faced the challenge of providing support to the millions of homeowners affected by the year's major hurricanes. The department provided mortgage insurance and foreclosure relief to affected homeowners and offered loans to local governments to rehabilitate communities and infrastructure. Over the course of 2017, HUD's Federal Housing Administration also endorsed over 1.2 million mortgages, accounting for nearly 15 percent of all mortgage originations nationwide.

Why you should care: The FHA's mortgage insurance program continues to allow millions of typically lower-income Americans to afford homes. Such mortgages accounted for nearly one-third of all new mortgages in the midst of the housing crisis nearly a decade ago and the ongoing decrease in share of FHA-backed mortgages across the market signals a strengthening economy.

Major headline at HUD: Just over a week ago, HUD announced it was pushing back the deadline for communities to submit their Assessments of Fair Housing until 2020. The Obama administration initiated the rule in 2015, forcing municipalities to map out a plan to address racial segregation using HUD funding.

Department of the Interior

Leader of agency: Secretary Ryan Zinke

What has changed: The Interior Department has moved to allow more mining in the U.S. and expedite permits for oil and gas drilling as part of the administration's effort to make the U.S. less dependent on oil and minerals from other countries. Zinke also made recommendations to alter four national monuments, including the controversial decision to shrink Bears Ears National Monument in Utah. The National Park Service, also part of Interior, has been considering proposals to raise fees at some of the most popular parks such as Yellowstone and the Grand Canyon to help pay for maintenance projects. Some parks have already announced fees will go up next year.

Why you should care: A lot of groups are concerned that more oil and gas mining in the U.S. could threaten the environment and say that activities such as drilling in the Arctic National Wildlife Refuge, which was recently approved, should not be allowed. Energy generated by the Interior Dept. through fossil fuels and renewable sources generates hundreds of billions of dollars for the economy every year. Zinke's proposal to change national monuments is also controversial because the law that allows the president to create national monuments is not typically used to make them smaller and a lot of advocacy groups and some companies plan to fight the decisions in court.

Department of Justice

Leader of agency: Attorney General Jeff Sessions

What has changed: Sessions has taken a hard-line approach toward illegal immigration and so-called "sanctuary cities." He has reshaped how the Justice Department approaches civil rights, including stepping away from broad investigations into how police departments address their communities and certain protections for LGBTQ Americans. However, the attorney general's relationship with Donald Trump has changed drastically over the past year, with the president frequently criticizing Sessions in public for his decision to recuse himself from federal probes tied to last year's presidential election.

Why you should care: For many Trump voters, how Sessions is changing the Justice Department is exactly why they voted for Trump in the first place. However, the president's constant pressure on Sessions and the department raises questions over whether top Justice Department officials can truly operate independently -- without fear of being fired.

Department of Labor

Leader of agency: Secretary Alexander Acosta

What happened: During his election campaign, Donald Trump advertised himself as a champion for the American worker and promised to roll back Obama-era regulations on businesses. Since becoming Republican controlled, the National Labor Relations Board has redefined the term "employer," giving companies more freedom in enforcing their handbook policies and making it more difficult for workers to create micro unions. The Department of Labor has also ruled that restaurants or other businesses can use tips however they like, as long as all workers are paid minimum wage. Supporters argue this money can now be divided up for dishwashers, line cooks and others. Those against it say the bosses may keep it for themselves. Since he took the office, job growth seen towards the end of his predecessor's tenure has continued. Unemployment has fallen to 4.1 percent, the lowest in nearly 17 years.

Why you should care: Whether you see it as crippling employee protections or easing heavy-handed micromanagement, the Trump administration is full steam ahead on rolling back regulations. The rulings are a predictable pendulum swing as Republicans take control from Democrats, but the question remains: how far will they go? Some are afraid of weakening unions, less overtime pay and policies protecting big corporations from damaging lawsuits. The Trump administration appears, unsurprisingly, in lockstep with business leaders, on most positions except immigration.

Department of State

Leader of agency: Secretary Rex Tillerson

What has changed: A self-described “unconventional” secretary of state, Rex Tillerson has spent the last year trying to remake the State Department through a “redesign” meant to make the foreign policy bureaucracy more efficient and up-to-date. That has meant a hiring freeze and cuts through attrition and buy-outs, which have been unpopular with many employees.

Tillerson has not been very popular with his boss either, as he and Trump clashed over their different styles and policy ideas. On the policy side, many of the Obama administration’s signature achievements have been undermined or dismantled, including Trump’s withdrawal from the Paris climate agreement and decertification of the Iran nuclear deal -- although Tillerson disagreed with both decisions. While he says he has no “wins” on the board, Tillerson has made gains in his campaign to ramp up international pressure on North Korea and strengthening the global coalition against ISIS.

Why you should care: Critics outside the department and inside blame Tillerson for a brain drain that has weakened the institution at a time of global upheaval, injuring U.S. standing in the world and demoralizing the diplomatic corps. Tillerson has also been confronted by allies rattled by Trump’s “America First” foreign policy doctrine, spending much of the year working on those strained relations, especially in Europe.

The peaceful pressure campaign against North Korea has achieved a sanctions regime far tougher than anything before, but the isolation and penalties have not slowed the regime’s nuclear and ballistic missile programs – leaving tensions at an all-time high, with few off-ramps. But dealing with that pressing danger and other challenges, including Russian aggression and Middle East turmoil, has been difficult as Tillerson battles a narrative that he doesn’t speak with Trump’s confidence or won’t last much longer in the role.

Department of Transportation

Leader of agency: Secretary Elaine Chao

What has changed: The Department of Transportation has slashed regulations — airline fee disclosures, data collection — and stepped up testing rules to battle opioids within the transportation sector. But this department will ultimately be judged on the administration’s ability to overhaul the nation’s infrastructure plan. After an election campaign hammering the nation’s airports, roads, bridges and security lines, President Trump says he and Secretary Elaine Chao will soon release a list of principles congress is to follow when forging a new infrastructure plan, a $1 trillion pledge dating back to repeated promises on the Trump campaign trail. Any Senate bill will need Democratic support, but the left, and others, have expressed confusion over the hodgepodge of federal, state, local and private funding sources proposed by the White House. The latest number from the White House on federal funding for the improvement plan is $200 billion.

Why you should care: In June, the White House’s self-proclaimed infrastructure week went a bit off the rails and became a punch-line for the never-ending haymaker headlines surrounding the administration. Candidate Trump's ambitious infrastructure plan was a rare one area of common ground for him and democrats, but the President has struggled to work on any significant bipartisan legislation thus far and distractions have prevented Trump from working on the one piece of legislation both parties should be able to get behind. White House aides have said the effort will be the top priority in 2018, but after a year of deeply divided politics, the question remains: can Trump heal old wounds and work with democrats to fix the country's struggling public works.

Department of Treasury

Leader of agency: Secretary Steven Mnuchin

What has changed: The Trump administration’s first year in the White House handed the Treasury Department, and the Internal Revenue Service, the most far-reaching rewrite of tax laws since 1986. The Republican-backed overhaul officially took effect January 1, and now the IRS is faced with revising, implementing and regulating new tax policy at breakneck speed to accommodate this year’s filing season.

Why you should care: Almost every American files taxes, so tax reform is bound to affect individuals and businesses. Some big businesses have already invested in their employees following the passing of the bill in December. Mnuchin claims individuals will see cuts as early as February, but experts point out that not everyone is guaranteed to get a tax cut. Experts also say implementing a new tax system could be too complex for small businesses to accomplish in a short amount of time.

Department of Veterans Affairs

Leader of agency: Secretary David Shulkin

What has changed: Enjoying bipartisan support in Congress, the VA was able to shepherd 10 significant new laws through Congress, including a reform on the appeals process to help lessen veteran wait times, revisions to the GI Bill that will be lucrative to veterans, improvements in veterans choice in health care, and perhaps most significantly, accountability reform that enables the VA to discipline, suspend and terminate employees easier and faster, something many had pushed for in the wake of a pattern of negligent treatment of veterans made public in 2014.

Why you should care: Overall, most veterans tell veterans service organizations their satisfaction with the VA has increased in the past few years. Still, veterans service organizations are pushing for the VA to develop more services for their changing veteran population, as female and minority veterans become a larger share of the whole, and they say that continuing budget issues threaten future stability of the VA. Some veterans still struggle for access to health care, especially in rural regions, and options for veterans to choose health care outside of VA health care providers remain complex and costly. We should expect to see continuing fights over choice, privatization and budget moving into 2018.

Drug Enforcement Administration

Leader of agency: Acting Director Robert Patterson

What has changed: During the waning hours of the Obama administration, under cover of darkness, alleged Mexican drug kingpin Joaquin “El Chapo” Guzman was extradited to the United States to face charges in federal court in New York. Guzman, who pleaded not guilty, faces 17 counts related to drug trafficking, fire arms, money laundering and murder> Despite El Chapo being brought to justice, the Drug Enforcement Administration and the incoming Trump administration would face a drug threat killing Americans at an unprecedented pace--the opioid epidemic. Cheap heroin and synthetic opioids like fentanyl-- 100 times more powerful than heroin and described by Attorney General Jeff Sessions as the “number one killer in America today” -- have flooded the U.S. illicit drug market.

Why you should care: Whether coming from the Mexican drug cartels or by parcel from manufacturers in China, fentanyl’s potency and addictive property were a lethal combination in 2016, contributing to a steep increase in drug overdose deaths which, according to the Centers for Disease Control, topped 64,000 that year. President Trump declared a public health emergency to address the opioid crisis. DEA has worked to shut down “dark web” marketplaces like Alpha Bay, where opioids and other illicit drugs were allegedly sold. The agency also added a new field division in Louisville, Kentucky, to focus on the acute opioid problem in West Virginia, Kentucky and Tennessee.

As 2017 ended, recreational marijuana became legal to purchase and use in California, while federal law continues to classify pot as a controlled substance, creating another challenge for the DEA.

Environmental Protection Agency

Leader of agency: Administrator Scott Pruitt

What has changed: The EPA has moved quickly to walk back regulations put in place by the Obama administration and reduce the agency's footprint. Administrator Pruitt has announced decisions to delay or revisit major regulations such as the Clean Power Plan and the Waters of the United States Rule that he says represent federal overreach and a burden on industry. Pruitt was also involved in the administration's decision to withdraw from the Paris climate agreement and under his administration the U.S. and EPA have been less involved in international conversations on how to combat climate change.

Why you should care: Many of the regulations the EPA has reversed were put in place the help the U.S. fight climate change that the previous administration considered dangerous to human health. The majority of climate scientists have found that if the global temperature goes up two degrees we could see more serious effects--including more dangerous floods, famine, and threats to crops. Environmental groups and scientists are concerned that removing regulations aimed at fighting climate change could make it more difficult to prevent that from happening and send a signal to other countries that the U.S. isn't serious about the issue.

Federal Bureau of Investigation

Leader of agency: Director Chris Wray

What has changed: Leadership--for one big thing. Chris Wray is now FBI director, after the controversial firing of James Comey. Even under Wray, though, the FBI has found itself in an unusual position as a political punching bag for the president and other Republicans. The FBI is facing questions over its integrity as never before, with the president and Republican lawmakers calling out a handful of specific FBI agents and personnel by name, including widely-heralded counterintelligence agent Peter Strzok and former FBI general counsel James Baker. About 35,000 people work for the FBI.

Why you should care: Trust in our nation's law enforcement is key to the rule of law. That's why, according to public statements at the time, Deputy Attorney General Rod Rosenstein appointed Robert Mueller as special counsel to take over the FBI's investigation of Russian meddling in last year's election. But as Comey tweeted just days before Christmas, "Sadly we are now at a point in our political life when anybody can be attacked for partisan gain. James Baker ... served our country incredibly well for 25 years and deserves better. He is what we should all want our public servants to be."

Federal Emergency Management Agency

Leader of Agency: Administrator Brock Long

What happened: As hurricanes Harvey, Irma, and Maria pummeled the southeastern coast, FEMA was on hand to distribute emergency supplies, and later, help families register for federal disaster assistance. At the peak of the storm response, the agency was burning through a whopping $200 million per day. FEMA also administered grants to offset the cost of extinguishing the wildfires that ravaged California this fall.

Why you should care: FEMA helps communities prepare for and respond to presidentially-declared disasters. In the wake of its longest continuous activation period to date, the agency is "tapped out," Long said, and several hundred exhausted employees have exceeded their overtime cap.

Immigration and Customs Enforcement

Leader of agency: Deputy Director and Senior Official Performing the Duties of the Director Thomas D. Homan

What has changed: ICE is divided into two parts - the immigration enforcement for the federal government and the chief investigative law enforcement agency for DHS. Since Trump took office, it’s the immigration side of the agency that has received the most notoriety -- carrying out the mission that undid the Obama-era enforcement priorities.

Trump’s executive order did away with enforcement priorities. ICE still carries out targeted enforcement (not random raids), but anyone found in violation of immigration law may be subject to arrest, detention and possible deportation. That led to 30 percent more immigration-related arrests in 2017 compared to the previous year, according to ICE’s end-of-fiscal-year report. “If you choose to violate the laws of this country, you should be concerned,” said Homan. A sentiment he has repeated many times.

ICE was directed to hire 10,000 new employees to focus on civil and criminal immigration enforcement. The agency has also been in direct, public confrontation with so-called “sanctuary cities” -- municipalities that choose not to comply with all ICE requests. "San Francisco’s policy of refusing to honor ICE detainers is a blatant threat to public safety and undermines the rule of law,” said Homan after the undocumented man accused of killing Kate Steinle was found not guilty. This case was a touchpoint for the administration, which said that the tragedy could have been prevented if San Francisco had turned the alien over to ICE.

Why you should care: Immigration enforcement has the potential to affect an estimated 11 million undocumented people already living in the U.S., their families, the U.S. economy and the countries to which they might be deported.

U.S. Coast Guard

Leader of agency: Commandant Paul Zukunft

What happened: Best known for their search & rescue missions, the Coast Guard struggled this year in Houston, where Hurricane Harvey dumped more than 50 inches of water, leaving many residents stranded on rooftops as water rose and emergency phone lines jammed. The Coast Guard was also among the first on scene in the U.S. Virgin Islands and Puerto Rico in the wake of Hurricanes Irma and Harvey, evacuating stranded residents and delivering supplies.

Why you should care: Search and rescue isn't the Coast Guard's only mission -- they also secure our nation's waterways and are the first line of defense against drug smugglers attempting to sneak cocaine and other illicit substances into the country by boat or submarine.

U.S. Forest Service

Leader of agency: Chief Tony Tooke

What has changed: The Forest Service and other agencies that manage public lands have been taking a more aggressive approach to prevent wildfires but have not seen an increase in resources as California and other states in the West see bigger fires each year.

Why you should care: The Forest Service plays a major role in fighting wildfires and managing public land that is prone to wildfires but has been warning for years that its budget is struggling to keep up as fires get bigger and more destructive.

U.S. Secret Service

Leader of agency: Randolph “Tex” Alles

What has changed: Coming fresh off of the relentless pace of an election year, the U.S. Secret Service began 2017 with managing security for the inauguration of President Trump. Though the election was contentious, the inauguration went off without any significant security related problems. It would be the final National Special Security Event for Director Joseph Clancy, who stepped down in March. A new director, former Marine General Randolph “Tex” Alles, brought the fresh perspective of an outsider to an agency known for its insular culture and habit of promoting from within. In December, the Secret Service conduced a first-of-its-kind, full-scale training exercise on the White House grounds, part of Alles’ influence on the agency to “train like we fight,” as he put it. After a string of fence jumping incidents in recent years, a new taller fence for the White House was finally approved and funded, with construction to begin in spring of 2018.

ABC News' Ely Brown, Jeffrey Cook, Jack Date, Erin Dooley, Stephanie Ebbs, Conor Finnegan, Cheyenne Haslett, Adam Kelsey, Mike, Levine, Whitney Lloyd, Luis Martinez, Meridith McGraw, Elizabeth McLaughlin, Geneva Sands and Alisa Wiersema contributed to this report.

This story is part of a week-long series examining the first year of the Trump administration.