His triumph over Hillary Clinton, not declared until well after midnight, will end eight years of Democratic dominance of the White House and threatens to undo major achievements of President Barack Obama. Trump has pledged to act quickly to repeal Obama's landmark health care law, revoke America's nuclear agreement with Iran and rewrite important trade deals with other countries, particularly Mexico and Canada.
ELECTION 2016 PHOTOS: VOTERS, CANDIDATES HEAD TO THE POLLS
As he claimed victory, Trump urged Americans to "come together as one united people" after a deeply divisive campaign.
Clinton called her Republican rival to concede but did not plan to speak publicly until later Wednesday. Trump, who spent much of the campaign urging his supporters on as they chanted "lock her up," said the nation owed Clinton "a major debt of gratitude" for her years of public service.
The Republican blasted through Democrats' longstanding firewall, carrying Pennsylvania and Wisconsin, states that hadn't voted for a GOP presidential candidate since the 1980s. He needed to win nearly all of the competitive battleground states, and he did just that, claiming Florida, Ohio, North Carolina and others.
Illinois Election Results
US Election Results, National Races
Global stock markets and U.S. stock futures plunged, reflecting investor concern over what a Trump presidency might mean for the economy and trade.
A New York real estate developer who lives in a sparkling Manhattan high-rise, Trump forged a striking connection with white, working class Americans who feel left behind in a changing economy and diversifying country. He cast immigration, both from Latin America and the Middle East, as the root of the problems plaguing many Americans and tapped into fears of terrorism emanating at home and abroad.
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Trump will take office with Congress fully under Republican control. GOP Senate candidates fended off Democratic challengers in key states, including North Carolina, Indiana and Wisconsin. Republicans also maintained their grip on the House.
Senate control means Trump will have great leeway in appointing Supreme Court justices, which could mean a shift to the right that would last for decades.
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Trump upended years of political convention on his way to the White House, leveling harshly personal insults on his rivals, deeming Mexican immigrants rapists and murderers, and vowing to temporarily suspend Muslim immigration to the U.S. He never released his tax returns, breaking with decades of campaign tradition, and eschewed the kind of robust data and field efforts that helped Obama win two terms in the White House, relying instead on his large, free-wheeling rallies to energize supporters. His campaign was frequently in chaos, and he cycled through three campaign managers this year.
His final campaign manager, Kellyanne Conway, touted the team's accomplishments as the final results rolled in, writing on Twitter that "rally crowds matter" and "we expanded the map."
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Clinton spent months warning voters that Trump was unfit and unqualified to be president. But the former senator and secretary of state struggled to articulate a clear rationale for her own candidacy.
The mood at Clinton's party grew bleak as the night wore out, with some supporters leaving, others crying and hugging each other. Top campaign aides stopped returning calls and texts, as Clinton and her family hunkered down in a luxury hotel watching the returns.
At 2 a.m., Clinton campaign chairman John Podesta told the crowd to head home for the night with the race not officially called, but the Democrat's fate all but certain.
Trump will inherit an anxious nation, deeply divided by economic and educational opportunities, race and culture.
Exit polls underscored the fractures: Women nationwide supported Clinton by a double-digit margin, while men were significantly more likely to back Trump. More than half of white voters backed the Republican, while nearly 9 in 10 blacks and two-thirds of Hispanics voted for the Democrat.
PHOTOS: Hillary Clinton on Election Day 2016
Doug Ratliff, a 67-year-old businessman from Richlands, Virginia, said Trump's election was one of the happiest days of his life.
"This county has had no hope," said Ratliff, who owns strip malls in an area badly beaten by the collapse of the coal industry. "Things will change. I know he's not going to be perfect. But he's got a heart. And he gives people hope."
Trump has pledged to usher in a series of sweeping changes to U.S. foreign policy, including building a wall along the U.S.-Mexico border and suspending immigration from countries with terrorism ties. He's also praised Russian President Vladimir Putin and spoken of building a better relationship with Moscow, worrying some in his own party who fear he'll go easy on Putin's provocations.
The Republican Party's tortured relationship with its nominee was evident right up to the end. Former President George W. Bush and wife Laura Bush declined to back Trump, instead selecting "none of the above" when they voted for president, according to spokesman Freddy Ford.
PHOTOS: Election Day for Republican nominee Donald Trump
House Speaker Paul Ryan, a reluctant Trump supporter, called the businessman earlier in the evening to congratulate him, according to a Ryan spokeswoman. Senate Majority Leader Mitch McConnell said the American people "have chosen a new direction for our nation."
Obama, who campaigned vigorously for Clinton throughout the fall and hoped his own rising popularity would lift her candidacy, was silent on Trump's victory, but he is expected to invite him to the White House this week. It will be a potentially awkward meeting with the man who pushed false rumors that the president might have been born outside the United States.
Democrats, as well as some Republicans, expected Trump's unconventional candidacy would damage down-ballot races and even flip some reliably red states in the presidential race. But Trump held on to Republican territory, including in Georgia and Utah, where Clinton's campaign confidently invested resources.
Clinton asked voters to keep the White House in her party's hands for a third straight term. She cast herself as heir to Obama's legacy and pledged to make good on his unfinished agenda, including passing immigration legislation, tightening restrictions on guns and tweaking his health care law.
But she struggled throughout the race with persistent questions about her honesty and trustworthiness. Those troubles flared anew late in the race, when FBI Director James Comey announced a review of new emails from her tenure at the State Department. On Sunday, just two days before Election Day, Comey said there was nothing in the material to warrant criminal charges against Clinton.
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