ABC News projects it was Pennsylvania that gave him the electoral votes he needed, and Biden, who was born in Scranton, has said his early life there has always been "a touchstone -- where I learned my values."
On Election Day, he had stopped at his childhood home and written on a living room wall: "From this house to the White House with the grace of God."
In some of his first words after being called the winner: more of that message.
"America, I’m honored that you have chosen me to lead our great county," Biden tweeted, with his profile changed to President-elect. "The work ahead of us will be hard, but I promise you this: I will be a President for all Americans — whether you voted for me or not."
In what many considered a referendum on Trump's handling of the pandemic and civil unrest across America, voters ultimately rejected Trump's disruptive leadership -- and in record-shattering numbers.
Trump falsely claimed victory in the early hours of Wednesday and then on Thursday, in stunning remarks for a president speaking from the White House, questioned the integrity of the American election process without presenting any evidence. It became clear, however, as mail-in and absentee votes continued to be counted, that Biden would narrowly take the Electoral College and also win more popular votes than any presidential candidate in history. Trump won the second-highest.
In another historic first: California Sen. Kamala Harris becomes the first woman and first woman of color to be elected vice president.
Biden pitched himself as a leader who would be "president for all Americans -- not just the ones who vote for me" -- in stark contrast to Trump who spoke of a country divided into blue states and red states.
Bringing the nation together, given all Americans have been through, will be a daunting and unprecedented challenge.
Turning 78 in just under three weeks, Biden will be the oldest president to take office.
His rise to the White House comes 48 years to the day he was first elected to the U.S. Senate.
He has persevered through repeated political setbacks and personal tragedy -- losing his wife Neilia and young daughter Naomi in a horrific 1972 car accident in which his young sons Beau and Hunter were severely injured. Beau died of a brain tumor in 2015 at age 46. Biden himself mostly overcome a stutter he's had since boyhood.
Many Democrats were less than completely confident in Biden's chances against a political force as formidable as Trump.
Burned by Hillary Clinton's unexpected presidential defeat in 2016, a race in which he had also contemplated running, many in his party had been wary, even as nationwide polls put Biden consistently ahead of Trump and with narrow leads in the battleground states that ultimately helped him to victory.
Though considered a front-runner even before he entered the Democratic race in April 2019, after raising his profile with former President Barack Obama, Biden, a moderate in a crowded field of primary contenders, faced pressure to take more progressive positions on health care and immigration that some worried might turn off voters and hurt his chances in a general election.
He has said he decided to challenge Trump after being provoked by his calling white supremacist demonstrators at a 2017 "Unite the Right" rally in Charlottesville, Virginia, "very fine people."
But Biden's long track record in public office made his campaign complicated: his opposition to federally mandated busing in the 1970s, his support for a 1994 crime bill seen as harmful to African Americans and his handling of Anita Hill's sexual harassment accusations against Supreme Court nominee Clarence Thomas in 1991 as then-chairman of the Senate Judiciary Committee.
Questioned about that record this May, Biden faced criticism when he told the host of "The Breakfast Club" radio program, which has a large African American audience, "If you have a problem figuring out whether you're for me or Trump, then you ain't Black." Biden later apologized.
As the primary race reached a critical point, Biden struggled.
It was a win in South Carolina on the last day of February -- propelled by the support of Black Democrats, the same demographic that sent him to the U.S. Senate in 1972 -- when his campaign bounced back. After a series of victories including a Super Tuesday triumph, Biden had a clear path to the nomination.
As the general election campaign was just getting started this past March, the spreading coronavirus pandemic caused much of the country to be on lockdown and forced Biden off the trail.
A nation in crisis, though, ultimately gave him the opportunity that led him to the White House.
As the pandemic worsened, Biden hammered its dark realities and pitched a national strategy to combat COVID-19, casting himself as a responsible counter to Trump's downplaying of the pandemic from early on.
Biden said that, even if he were elected, ending the pandemic wouldn't be "like flipping a switch," but unlike Trump, he has offered a plan, so Americans might expect a much different federal response to COVID-19 come January.
While Trump ran on rejecting testing and often mocked him and others for wearing masks, Biden has proposed doubling the number of testing sites in the U.S., investing in rapid and at-home tests and asking governors to mandate facial coverings in public when distancing isn't possible, among other measures.
As Biden tried to take Trump on the issues like his handling of the pandemic, Trump made mostly personal attacks -- not only on Biden but on his family.
Throughout the campaign, Trump and his allies sought to weaponize the foreign activities of Biden's only surviving son, Hunter, arguing his business dealings in Ukraine and China were a conflict of interest for his father. But no evidence has emerged that Hunter Biden's private business deals influenced Joe Biden's actions or U.S. foreign policy as vice president -- and he has said they did not.
This summer, to promote Democratic and racial unity, Biden chose Harris, who had confronted him during the primaries about his his record on busing, as his running mate, the first Black woman and Asian American to join a major party's presidential ticket.
When accepting the Democratic nomination in August, Biden outlined what he deemed were the four crises facing the country: the coronavirus pandemic, economic collapse, racial injustice and climate change -- issues he's promised to push in legislation in his first 100 days, but his chances success could depend heavily on whether Democrats control the Senate as well as the House, which is still possible with undecided races in Georgia.
He has already unveiled a sweeping new proposal that called for the U.S. to achieve a carbon-free power sector by 2035 and a $2 trillion investment over his first four years in office in green energy and infrastructure to combat the threat of climate change.
Biden has said he would eliminate the Trump tax cuts that benefited corporations and wealthy Americans, arguing it's time for them to contribute their "fair share," but has promised he wouldn't raise taxes on households making less than $400,000 a year.
In the wake of protests across the country over racial inequality this summer, Biden did not join calls to defund police departments, but advocated for providing an additional $300 million in funding for community-based policing, as well as pairing police with mental health experts to be able to better address community needs -- measures he's vowed to prioritize.
Biden has made several other promises of actions he'd take on "Day One" of his presidency, including rejoining the World Health Organization and the Paris Agreement on climate, and sending an immigration bill to Congress creating a pathway to citizenship for so-called "Dreamers," young undocumented immigrants who came to the U.S. as children and have lived most of their life here.
Biden also kept the Affordable Care Act at the top of his message, telling voters he would attempt to make the program easier to navigate with more choices and provide a public option for patients to buy into, while slamming the Trump administration for its efforts to entirely dismantle the program headed to the Supreme Court next week.
Biden still has work to do, particularly among the Latino community where his backing among the population fell short of the support that Clinton got in 2016. The Latino community has warned Democrats to be mindful of the diversity and complexity of their vote, ranging from conservatives to young liberals -- a top-mind lesson for Biden as he tries to unite a diverse and divided country.
Americans chose him as a clear alternative to Trump: decency, even if flawed, over divisiveness.
After nearly half a century on the national stage -- amid a raging pandemic -- for Joe Biden, the "boy from Scranton," the moment has come.
ABC News' Molly Nagle, John Verhovek and Kendall Karson contributed to this report.