WASHINGTON — A vast, excited crowd of more than a million bore witness yesterday to a transfer of American power like none before it. The blare of regal trumpets and thunder of cannon were familiar. The transition from Republican to Democrat, and gray hair to dark, had happened before.

But this was white to black, a shattering of racial barriers finally made complete when Barack Obama made it through a bumbled oath-taking, delivered a momentous-by-definition speech and got back to being his unflappable self.

The Democrat who charged onto the national scene saying this was not a nation of red states and blue states, but the United States, became president while wearing a red tie, the Republican color.

Republican George W. Bush, president no more, wore a blue tie, the Democratic color. They embraced at the Capitol and walked out together.

"Everybody is behind him," said Mikki Hill, 26, who traveled from Winston-Salem, N.C., and marveled at the multiracial multitudes. "Everybody's come from as far as the Earth is wide."

So it seemed on a day when change and continuity marched together in a spectacle of pageantry and raw emotion.

A couple of hours after being sworn in, Obama and his wife, Michelle, got out of their armored limousine — reportedly nicknamed "The Beast" by the Secret Service — bearing the license plate USA 1 and strolled together down the middle of Pennsylvania Avenue, holding hands and waving during the spirited inaugural parade. People along the packed parade route screeched in greeting.

The racial milestone lent a deeply personal dimension for many in the crowds as well as a historical landmark for all.

"I've been real emotional all morning thinking about my grandmother and the heroes whose shoulders we stand on," said Lyshundria Houston, 34, here from Memphis, after more than 20 hours of travel. Houston, who is black, said: "They'd be so proud."

Energized by the moment, hordes clogged the scene, enduring below-freezing temperatures. Starting before dawn, with the Capitol bathed in lights, they streamed from jammed subway stations and thronged past parked buses, emergency vehicles and street vendors to Pennsylvania Avenue and the National Mall.

Ticket holders approaching the inaugural site filed through security sweeps in lines coiled like cinnamon rolls.

They cheered dignitaries as they came on to the inaugural stand at the Capitol. Obama walked quietly and with the merest stirring of a smile through the halls to his position on the stand and his place in history.

The crowd erupted in jubilation as he strode out.

Former Presidents Bill Clinton and George H.W. Bush, the latter walking haltingly with a cane, embraced.

Roland Pool, 47, a white social worker from Santa Fe., N.M., sized up the new president as "solid and upfront. He deals with a million people with a smile — and stoicism, too."

Elizabeth Courtman, 24, who recently moved to Washington from southern Alabama and supported Republican John McCain for president, said she came away with something to tell her children and grandchildren someday. "There's no denying the spectacle," said Courtman, who is white. "Our generation has never seen anything like this."

The grace notes of the day were not shared by all. A wave of boos greeted the introduction of Bush and his outgoing vice president, Dick Cheney, who was in a wheelchair. "Na na na na, hey hey, goodbye," some people chanted.

Bush and his wife, Laura, were soon out of town. At Andrews Air Force Base, Md., they boarded a plane and took off for Texas.

The White House Web site switched to Obama from Bush before the new president had concluded his inaugural address.

"Change has come to White House.gov," said the first blog of the Obama team.

At the Capitol, a protective Plexiglas shield extended about 2 feet up from the balustrade around the speaker's platform for Obama's speech.

The district fire department responded to dozens of calls from people falling down or complaining of being cold, D.C. fire and EMS department spokesman Alan Etter said. About two dozen were hospitalized.

Etter said medical personnel were having trouble getting to people quickly around the mall because of the throngs of people, but he added that everyone who needed help has eventually received treatment.

By 4 a.m., lines of riders had already formed in suburban parking lots for the Metro transit system, which opened early and put on extra trains for the expected rush. Many parking lots filled up and had to be closed.

Streets around the Capitol quickly filled with people, and security checkpoints were mobbed. The cold registered at a frosty 25 degrees at late morning, rising to 28 at the time of the swearing-in.

Warming tents and other facilities on the Mall were late opening because traffic and crowds delayed staffers from reaching them. At one spot, 150 people waited to buy a cup of coffee.

A flea-market atmosphere prevailed on downtown streets, with white tents set up to sell Obama T-shirts and mugs as well as food, bottled water, snacks, scarves and footwarmers. The scent of grilled sausages and steaming Chinese food greeted those who walked toward the parade route, more than six hours before Obama would pass by.

As waves of people moved through security screenings, they scrambled for prime viewing spots along Pennsylvania Avenue — sitting on the curb, staking out plots of grass, or clambering on cold metal benches.

Real estate appraiser Denise Grandberry of St. Louis stood near the mall with her niece Murphy and daughter Nikki and talked about all the foreclosed homes she's seen in her work. "I've seen the remnants of peoples' lives," she said. "I have hope now and I think the nation has hope."

Some 410,000 people had entered Washington's Metro transit system by 9 a.m., an extraordinary number, transit officials said. "God bless them, they came out in this weather," said Robyn Ahlstrom, a volunteer with the Presidential Inaugural Committee.

The joyous mood of many was tempered for some by delays and dashed expectations.

At a security checkpoint for Obama supporters holding tickets for the swearing-in ceremony, thousands queued before 8 a.m. But the crowd grew frustrated, pushing forward as noon approached, and officials neither admitted anyone nor provided an explanation, said Beth Zollars, an Obama supporter from Leawood, Kan.

"People were waving their purple tickets in the air, saying, 'Please let us in, please let us in," said Zollars, who served on a fundraising committee for the Obama campaign in Kansas City, Mo. "It was just a terrible sense of disappointment because we took a lot of time and money and energy to get here, because you feel like you're missing the historic part of why you came here."