Obama strode on stage and into the history books becoming the first black American to be nominated by a major political party as the nation's commander-in-chief.
Tonight, 84,000 Democrats at Denver's Invesco Field were dancing and cheering as he accepted their presidential nomination.
Walking out to the podium, he appeared briefly humbled as the crowd, waved "Change" signs and American flags, and gave him an overwhelming standing ovation, chanting "Yes, we can! Yes, we can!"
"With profound gratitude and great humility, I accept your nomination for the presidency of the United States," Obama told an ecstatic, cheering crowd of Democratic party elite, delegates, civil rights leaders and celebrities including Oprah Winfrey.
Adding to the poetry and symbolism of the event, Obama's accomplishment arrived on the 45th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech and march on Washington.
Looking around the filled stadium at people dancing, cheering, and applauding, Texas state repesentative and delegate Mike Villarreal had tears in his eyes.
"I want to be able to tell my kids I was here when a black man and a white man got elected to lead our party," Villarreal said, "And I'm part of that for them."
Obama began with a nod to his vanquished primary rival New York Sen. Hillary Clinton and her husband former President Bill Clinton, who delivered solid speeches of endorsement at the Democratic Convention this week, despite a bitter primary battle that left lingering tensions for months.
"Let me express my thanks to the historic slate of candidates who accompanied me on this journey, and especially the one who traveled the farthest -- a champion for working Americans and an inspiration to my daughters and to yours -- Hillary Rodham Clinton," Obama said.
"To President Clinton, who last night made the case for change as only he can make it; to Ted Kennedy, who embodies the spirit of service; and to the next Vice President of the United States, Joe Biden, I thank you. I am grateful to finish this journey with one of the finest statesmen of our time, a man at ease with everyone from world leaders to the conductors on the Amtrak train he still takes home every night," Obama said of his vice presidential candidate.
In a soaring speech Obama outlined economic hardships Americans face and blamed President Bush's presidency.
"Tonight, more Americans are out of work and more are working harder for less. More of you have lost your homes and more are watching your home values plummet. More of you have cars you can't afford to drive, credit card bills you can't afford to pay and tuition that is beyond your reach," Obama said.
"These challenges are not all of government's making. But the failure to respond is a direct result of a broken politics in Washington and the failed presidency of George W. Bush," the Democratic presidential candidate said.
"America, we are better than these last eight years. We are a better country than this ... We are here because we love this country too much to let the next four years look just like the last eight. On November 4th, we must stand up and say: 'Eight is enough.'"
"It's time to change America, and that's why I'm running for president of the United States," Obama said to cheers.
"I realize that I am not the likeliest candidate for this office. I don't fit the typical pedigree, and I haven't spent my career in the halls of Washington," he said.
"But I stand before you tonight because all across America something is stirring. What the nay-sayers don't understand is that this election has never been about me. It's been about you," Obama said.
"For eighteen long months, you have stood up, one by one, and said enough to the politics of the past. You understand that in this election, the greatest risk we can take is to try the same old politics with the same old players and expect a different result. You have shown what history teaches us that at defining moments like this one, the change we need doesn't come from Washington. Change comes to Washington. Change happens because the American people demand it because they rise up and insist on new ideas and new leadership, a new politics for a new time."
In his Democratic nomination acceptance speech, Obama sharply contrasted his candidacy with Arizona Sen. John McCain, mentioning his Republican rival about 21 times.
"John McCain has voted with George Bush ninety percent of the time," Obama said. "Senator McCain likes to talk about judgment, but really, what does it say about your judgment when you think George Bush was right more than ninety percent of the time? I don't know about you, but I'm not ready to take a ten percent chance on change."
Rumors swirled at the convention center that McCain would announce his vice presidential candidate tonight.
However ABC News' George Stephanopoulos reports a senior campaign official said, "There will be no announcement tonight. There will be no leak tonight. This is Barack Obama's night. His nomination is a singular achievement. Tonight's his night to make his case."
Obama aggressively argued that an Obama White House would keep Americans safe. It's a weak spot for Obama, with the latest ABC News/Washington Post poll showed McCain leading Obama by 2-1 margins as more knowledgeable on world affairs and as better-suited to be Commander-in-Chief.
Taking the fight to McCain, Obama aggressively attacked the GOP nominee, and defended Democrats' ability to keep the nation safe.
"John McCain likes to say he'd follow Osama bin Laden to the gates of hell. But he won't even follow him to the caves he lives in," Obama said.
"We are the party of Roosevelt. We are the party of Kennedy. So don't tell me that Democrats won't defend this country," Obama said. "Don't tell me that Democrats won't keep us safe. The Bush-McCain foreign policy has squandered the legacy that generations of Americans -- Democrats and Republicans -- have built, and we are to restore that legacy."
"As Commander-in-Chief, I will never hesitate to defend this nation, but I will only send our troops into harm's way with a clear mission and a sacred commitment to give them the equipment they need in battle and the care and benefits they deserve when they come home," he said.
Obama also pledged to "end this war in Iraq responsibly, and finish the fight against al Qaeda and the Taliban in Afghanistan" -- using softer language than his calls for "immediate" withdrawal of US troops in Iraq at the beginning of his campaign.
Obama ended his speech with a rousing request for people to vote for him in November.
"America, we cannot turn back. Not with so much work to be done. Not with so many children to educate, and so many veterans to care for. Not with an economy to fix and cities to rebuild and farms to save. Not with so many families to protect and so many lives to mend. America, we cannot turn back. We cannot walk alone. At this moment, in this election, we must pledge once more to march into the future. Let us keep that promise -- that American promise -- and in the words of Scripture hold firmly, without wavering, to the hope that we confess. Thank you, God Bless you, and God Bless the United States of America."
Fireworks went off at the end of his speech red and blue star shaped confetti fell.
Obama was joined on stage by his wife Michelle Obama, their daughters Mailia, 10, and Sasha, 7, and his vice presidential candidate Joe Biden and his wife Jill.
Despite the Martin Luther King anniversary, Michelle Obama told ABC's Charlie Gibson in an interview that aired on World News Thursday that the speech would be be geared toward all Americans.
"You know, I think that the issues that are effecting the country really transcend race and gender and age. That's what I've been finding throughout this campaign," Michelle Obama told Gibson.
"When someone is struggling to pay to put gas in their car, when a person has lost their job, and doesn't have health care, and they're worried about their kids' college education, those problems know no racial boundaries ... we're suffering these issues equally, and if we're going to fix them, we're going to have to work together."
Michelle Obama said she hasn't seen a draft of the speech and stopped her husband when he started reading it to her.
"I like to, to feel the impact like everyone else," the potential first lady told Gibson.
She sat beaming as she listened to his speach with her daughters beside her.
Sen. Hillary Clinton sat listening in a skybox, but neither her daughter Chelsea, nor her husband were with her.
She sat with Ohio Gov. Ted Strickland, New York Gov. David Paterson, former Iowa Gov. Tom Vilsack, New Jersey Gov. John Corzine, Maryland Gov. Martin O' Malley, and LA Mayor Antonio Villaragosa, and her childhood best friend Betsy Ebeling and her staff.
In an earlier speech to the packed stadium crowd, former Vice President Al Gore compared the choice in this election to the choice in 2000 when he ran against then-Gov. George W. Bush, knocking McCain for "recycling" the same old Bush-Cheney policies.
"Today, we face essentially the same choice we faced in 2000, though it may be even more obvious now, because John McCain, a man who has earned our respect on many levels, is now openly endorsing the policies of the Bush-Cheney White House and promising to actually continue them. The same policies all over again?" Gore said.
"Hey, I believe in recycling, but that's ridiculous."
"With John McCain's support, President Bush and Vice President Cheney have led our nation into one calamity after another because of their indifference to fact; their readiness to sacrifice the long term to the short term, subordinate the general good to the benefit of the few and short-circuit the rule of law."
Gore also said if he won in 2000, the nation wouldn't still be in Iraq.
"Take it from me, if it had ended differently, we would not be bogged down in Iraq, we would have pursued bin Laden until we captured him. We would not be facing a self-inflicted economic crisis; we would be fighting for middle-income families. We would not be showing contempt for the Constitution; we'd be protecting the rights of every American regardless of race, religion, disability, gender or sexual orientation. And we would not be denying the climate crisis; we'd be solving it."
Obama spoke to the crowd on an "in the round," surrounded by the crowd and flanked by columns and a large screen.
The McCain campaign had labeled the stage on which the Democratic contender will speak the "temple of Obama," likening Obama to a rock star and continuing to criticize him as a celebrity rather than a serious candidate for the White House.
Senior Obama campaign officials said the stage is "simple" and "serious" and told ABC News they are not going to apologize for what they called an "enthusiasm gap" between Obama and McCain supporters.
Obama's acceptance speech was moved from the Pepsi Center in Denver, which can accommodate about 20,000 people, to the football stadium earlier this summer.
In a clever political move, the McCain campaign released Thursday night a one-evening-only ad airing on national cable that congratulates Obama on his historic nomination.
"Sen. Obama, this is truly a good day for America," McCain says in the ad. "Too often the achievements of our opponents go unnoticed. So, I wanted to stop and say, congratulations."
"How perfect that your nomination would come on this historic day," McCain continues to say in the ad. "Tomorrow, we'll be back at it. But tonight, senator, job well done."
Obama's campaign said 80,000 people in 48 hours had requested a ticket to Thursday's event and they claim they turned away tens of thousands of people to make space for delegates and other leaders.
A majority of the packed stadium -- 65 percent of the people -- were from the Southwest region including Colorado, Nevada and New Mexico -- states thought to be in play for either Democrats or Republicans in November.
Millions more watched from home and online with Obama scheduled to speak in primetime. Jennifer Hudson sang the national anthem and Sheryl Crow and Stevie Wonder performed.
Viewing the speech as a "persuasion opportunity" to reach out to independent voters in Colorado, the campaign put some of the tens of thousands of people in the stands to work -- calling voters, texting friends -- and training them how to register voters in their area.
Just around 8:00 p.m. ET Obama supporters received this text message: "Final night of convention is tonight -- don't miss Barack's speech! To get involved locally, REPLY: VOL plus your FIRST NAME and TOWN (ex: VOL Ann Chicago)."
Inside the stadium, Denver resident Sandra Bridge, 63, told ABC News, "This is the most exciting period of my life."
"Martin Luther King's dream seemed like it had slipped away," Bridge said. "The dream is real now."
During the convention program, Georgia Congressman John Lewis -- the last living person who spoke at the Martin Luther King, Jr march on Washington, D.C., in 1963 -- introduced a moving video tribute to King, and called the nomination of Barack Obama "a major down payment" on the fulfillment of King's dream.
"As a participant in the civil rights movement, I can tell you the road to victory will not be easy. Some of us were beaten, arrested, taken to jail, and some of us were even killed trying to register to vote. But with the nomination of Senator Barack Obama tonight, the man who will lead the Democratic Party in its march toward the White House, we are making a major down payment on the fulfillment of that dream," said Lewis, who was brutally beaten marching in Selma, Alabama.
Lewis urged attendees to do everything they can to elect Obama.
"On November 4th, we must march in every state, in every city, in every village, in every hamlet; we must march to the ballot box. We must march like we have never marched before to elect the ext President of the United States, Senator Barack Obama."
Setting the stage for the marquee speech of the Democratic National Convention was an Obama campaign "unity" breakfast with black leaders Thursday morning.
About 500 black delegates, civil rights leaders including Martin Luther King Jr.'s daughter Bernice King and the Rev. Al Sharpton, as well as celebrities like Oprah Winfrey's best friend Gayle King and actors Cicely Tyson, Lou Gossett Jr., Alfre Woodard and Blair Underwood, gathered for breakfast in Denver.
"I hope I can remain upright in my chair," King told ABC News of Obama's speech Thursday night. "When people say 'I have a dream' today, I say my dream is coming true," she said. "I knew this day would come and I still know it."
Oprah caused a stir when she walked through the stadium, briefly stopping by the ABC News workspace to say hello to ABC's Robin Roberts, George Stephanopoulos, and David Westin. "She wouldn't miss it," Gayle told ABCNews.com earlier of Oprah.
For many civil rights advocates, the day was charged with emotion.
"It reminds me of my youth," said Maude Beavers-Barker, 73, now a California resident who organized bus loads of grass-roots volunteers from Milwaukee to Washington in 1963 to march with King and hear him speak.
"I'm in awe today," she said of Obama's nomination.
Other prominent African-Americans at the breakfast expressed disbelief.
"I'm numb, I'm absolutely numb," Tyson told ABCNews.com. "I never ever dreamed that in my lifetime I would be witnessing this."
The Rev. Otis Moss Jr., a civil rights leader, told ABC News that he was at the march in 1963 several feet from the platform and looking directly in the face of King when he made that historic address. Moss said the day could not be more fitting.
"Sen. Obama represents the very thing that Dr. King articulated not only in that speech but in his entire life and work," Moss said.
Firing up the crowd, the Rev. Joseph Lowery, president of the Coalition for the People's Agenda, said Obama doesn't have to be a civil rights leader between now and November.
"He can go ahead and be president and leave the agitating to us," he said to cheers in the crowd.
"The most important thing he can do for the nation is get elected," Lowery said.
Bernice King also brought the crowd to its feet, arguing that despite Obama's historic accomplishment, her father's work is far from done.
"He declared that he may not get there with us," she said, "and we are on our way to the promised land but we are not there yet and our next step is unity."
"Let us be satisfied when our young men are going to college not going to jail," she said to loud cheers and applause. "The movement is not there. Let's continue the movement!"
Sharpton brought the crowd again to its feet with a verbal slap against President Bush.
"The media keeps talking about passing the baton," he said of news coverage about former President Clinton's solid endorsement Wednesday night of Obama. "The only baton that we're going to pass is from George Bush to Barack Obama."
Sharpton said civil rights leaders will go in November to "states that seem to have difficulty counting votes."
"We're going to make sure that the names of African-American voters don't mysteriously disappear," he said. "Not this time! We will not be divided. Not this time!"
Others expressed pride in Obama for being the first black to be nominated for president on a major party ticket.
"I just wish my dad was here to see this," said actress Holly Robinson Peete, whose father, television producer Matt Robinson, marched on Washington.
"He would be so proud of Obama," she said.
"To have it occur on the 45th anniversary of the march on Washington that it was destined to be. It could have never been anyone else," Tyson said.
"My old friend Jane Pitman used to say that when a child is born folks look into its face and ask, 'Are you the one? Are you the one? Well, he is definitely the one," she said.
Other speakers echoed that Obama's candidacy alone isn't enough.
Charles Steele of Georgia's Southern Christian Leadership Conference said Obama is about to make history but the fight isn't over.
"We might quit at this point but we can't quit. We can't let Martin Luther King and other civil rights leaders in the movement down," Steele said. "I challenge you to think about this moment not as a fulfillment of the dream but an important step along the way."
Steele said blacks still have to fight on a daily basis against higher rates of poverty and racism.
Georgia delegate Aaron Johnson told ABCNews.com, "Just because one out of a hundred makes it doesn't make it easy for the other 99."
"While there is a chance and there is more hope for people, we still have a long way to go as a people as a nation," Johnson said, "As long as there is poverty, and there are people who don't have and people who can't have, there's always going to be room for improvement."
ABC News' Jake Tapper, Kate Snow, Karen Travers, John Berman, Tahman Bradley, and Nitya Venkatarman contributed to this report.