President Barack Obama gives his inaugural address at the U.S. Capitol in Washington, Tuesday, Jan. 20, 2009, after being sworn in as the president of the United States.

Washington ? A vast, excited crowd of more than 1 million bore witness Tuesday 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.

The racial milestone lent a deeply personal dimension for many in the crowd 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, Tenn., after more than 20 hours of travel. Houston, who is black, said: “They’d be so proud.”

Coming from the city where Martin Luther King Jr. was assassinated, she reflected on the civil rights movement on her way to the parade, and said: “Sometimes that makes the cold go away.”

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.

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.

Nor did everything go off without a hitch on the stand.

Chief Justice John Roberts got a phrase out of order when leading Obama in the Constitution’s 35-word oath. That prompted a pregnant pause from Obama at the very brink of becoming president. The two men caught up with each other later at the congressional lunch and chatted, smiling.

Bush and his wife, Laura, were soon out of town. At Andrews Air Force Base, they boarded a plane — no longer called Air Force One because he is no longer president — waved 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 WhiteHouse.gov,” said the first blog of the Obama team.

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

Muhammad Ali took his seat on the platform, as did actor John Cusack and director Stephen Spielberg. A huge cheer rose from the Mall as the image of Sen. Edward M. Kennedy flashed on jumbo TV screens showing the veteran Massachusetts Democrat, who is fighting brain cancer, heading toward his seat on the inauguration stand.

The district fire department responded to dozens of calls from people falling down or complaining of the 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.

“Obviously the crush of people downtown is making it very challenging,” Etter said. “We’re doing the best we can.”

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

Real estate appraiser Denise Grandberry of St. Louis stood on 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.

Medical personnel struggled because of the crush of the crowd. One officer, with a patient he described as having had a seizure, tried to find out when an ambulance would arrive and couldn’t. “She’s been here nearly an hour,” the officer radioed. “She really needs to get to the hospital.”

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

Alice Williams, a 51-year-old teacher of gifted children from Kansas City, Mo., had the coveted purple ticket that would place her in front of the Capitol, but got caught in the crowd bottleneck and was stuck a half mile away.

“We got blocked off; there was too much traffic and no guidance,” she said forlornly. “I’ve been walking for an hour and a half. All I want to do is see my president sworn in.”

The cold was also taking its toll.

Shelton Iddeen, 57, of Greensboro, N.C., arrived at the Mall at 4 a.m. and huddled in front of an ambulance to warm up.

“My hands feel really bad; you can’t feel your toes,” he said. “I’m more concerned about other people, the elderly and the young. I’ve seen a lot of people here really suffering.”

Others were unfazed.

Faosat Idowu of Lagos, Nigeria, had tickets for the inauguration but couldn’t get through the crowds at five different entrances between the White House and Capitol Hill. She ended up walking in a highway tunnel that normally carries Interstate 395 under the Capitol grounds, closed for this one day to all but pedestrians. She wore a bright red scarf and hat adorned with dozens of green patches bearing Obama’s face and the words, “Africans for Obama.”

“It’s part of the excitement,” Idowu said. “I don’t mind it at all.”

Onjali Bodrul flew from London to see a man whose career she and her friends have followed since she was a political science student at Oxford four years ago. “He’s the first man in politics in a long time we don’t hate,” she said. “It’s like a football match, it’s so exciting.”