Hundreds of thousands of people have gathered on Washington's national mall for the inauguration of Barack Obama as America's 44th president. The crowd is expected to swell to an estimated one to two million looking on as Mr. Obama becomes the first African-American to take the presidential oath of office.
As daylight broke over Washington, tens of thousands had already packed the vast mall stretching out from the U.S. Capitol building where Barack Obama will take the oath of office.
Beginning in the early hours, Washington's subway system was crammed with people making their way into the city to observe the inauguration.
One woman from Pennsylvania said she was overwhelmed to be taking part in the historic event.
"I could not be happier or more proud," she said. "I am an 81-year-old black lady who has seen an awful lot in my lifetime. And never, in all of my years, did I think that this day would come, and one of us would be in the White House, doing more than taking care of someone."
President-elect Obama and his wife Michelle left Blair House to attend St. John's Episcopal Church early in the day where they participated in a brief service attended by family and friends.
Then the Obamas went to the White House for a brief visit with soon-to-be former President George W. Bush and his wife Laura, before heading to the Capitol, where the oath of office is administered.
Later, the traditional inaugural parade will wind its way through central Washington, as then President Obama makes his way to the White House to assume office.
Among the hundreds of thousands of people jamming the national mall was Byron Miller and his family visiting from San Antonio, Texas.
He says Barack Obama's journey to the presidency is a feat for all Americans to savor, but one that holds special meaning for those who descended from slaves.
"We have gone from emancipation [from slavery] to inauguration. My emotions run from exuberance to just [being] excited," Miller said.
In events leading up to the historic occasion, Mr. Obama hosted a dinner for another African-American trailblazer - retired General and former Secretary of State Colin Powell.
Reflecting his hope to be able to change the tone of politics in Washington and usher in a new era of bipartisanship, Mr. Obama also hosted a dinner for Senator John McCain, who he defeated in the November election.
Mr. Obama is expected to use his inaugural address to reassure Americans amid the worst economic crisis since the Great Depression of the 1930s, and also urge them to greater public and national service.
During a visit to a Washington shelter for homeless youth, Mr. Obama said Americans need to adopt a long-term attitude of serving others and their country.
"If we are waiting for someone else to do something, it never gets done, we are going to have to take responsibility [for our nation's well-being]. All of us," Mr. Obama said. "And so this is not just a one-day affair."
His speech is also expected to pay tribute to the slain civil rights leader Reverend Martin Luther King, Jr., without whose life's work and sacrifice Mr. Obama's rise to power might not have been possible.
After the ceremony, Mr. Obama attends a luncheon with members of Congress in the U.S. Capitol before heading down Pennsylvania Avenue as part of the traditional inaugural parade.
But the transition from the Bush administration to the Obama administration will already be underway even before Mr. Obama arrives at the White House.
About 20 officials who will serve the new president will leave the Capitol immediately to take up their responsibilities and prepare for a busy first day of the new Obama administration.