Clinton, who had hoped to wake up as the first female president-elect, instead stood before traumatized campaign workers and supporters in New York to deliver her first public reaction to a loss that has sent shockwaves around the world.
"I still believe in America and I always will. And if you do, then we must accept this result and then look to the future," said Clinton, at times choking back emotion. "Donald Trump is going to be our president. We owe him an open mind and the chance to lead."
Her speech marked a bitter conclusion to a campaign that promised history but instead will be remembered for failing to fully energize Democratic voters and for squandering the party's traditional heartlands in states like Pennsylvania and Wisconsin.
It also marked the final act on the national stage of the Clinton double act, the political partnership between former President Bill Clinton and the former first lady and secretary of state that had seemed poised for a remarkable comeback, 16 years after they left the White House.
Campaign staffers had spoken throughout Clinton's presidential bid of the extreme pressure many of them felt in facing Trump, whom Clinton argued was temperamentally and intellectually unfit for the presidency and to be in charge of the US nuclear arsenal.
Now she is under pressure to call on a nation, split almost exactly down the middle, to unite behind the next president.
It will not be the first time Clinton has tasted the pain of ending a defeated presidential campaign. In 2008, she folded her primary bid against Barack Obama in Washington and bemoaned her failure to break the "highest and hardest glass ceiling" by becoming the first female president. That was to be her fate again in 2016, though the personal recriminations are likely to be even more intense this time given that Trump is seen by many Democrats as antithetical to American values.
Robby Mook, Clinton's campaign manager, emailed all campaign staffers Wednesday morning inviting them to join Clinton at the speech, campaign aides said.
The remarks were billed as the former Democratic nominee's goodbye to staff and as a way for her to lay out a way forward for Democrats and the country.
Dozens of Clinton staffers were waiting to get into the event an hour before the start. Many were hugging and some were crying.
"I'm still in shock," said one aide.
Clinton called Trump in the early hours of Wednesday to concede defeat after he shattered her Democratic firewall in the Midwest and swept to victory after the most vitriolic general election in generations.
But she did not appear at her election night party in New York. At the time, her campaign chairman John Podesta explained that the campaign wanted to ensure that every vote in still undeclared states was counted -- though her position already seemed hopeless.
Much of the seating at Clinton's remarks was for staff and aides and the campaign was treating it as a farewell to the people who have spent the better part of two years working on her behalf, an aide said.
Democratic vice presidential nominee Tim Kaine also was on hand, a campaign aide said. The Virginia senator was not with Clinton Tuesday night.
Trump's campaign manager, Kellyanne Conway, said Wednesday that she was with Trump when Clinton's close aide, Huma Abedin, called to say her boss wanted to talk to the president-elect.
"I handed him the phone and they had a maybe one-minute conversation, very gracious, very warm. I heard Mr. Trump's side of it," Conway told CNN's Alisyn Camerota on "New Day. "He commended her for being smart and tough and running a very hard-fought campaign. And I am told Secretary Clinton congratulated Donald Trump on his victory, and conceded to him," Conway said.