WASHINGTON -- Festive crowds jammed the sidewalks yesterday along the city's rejuvenated U Street corridor, once known as the nation's Black Broadway before it was ravaged in 1968's race riots. The biggest throng was in front of Ben's Chili Bowl, where President-elect Barack Obama visited Friday.

Less than three miles away, work crews put finishing touches on scaffolding at the Capitol, ordinary citizens strolled along the National Mall and Mr. Obama visited wounded soldiers and homeless teens in a day of service honoring Dr. Martin Luther King Jr.'s legacy -- before appearing at a dinner for his Republican opponent, Sen. John McCain.

It was all prelude as the nation prepared for an inauguration like no other, that of its first black president.

"I just wanted to come here and feel the energy, the happiness. Because he was here, I wanted to be here," said Kym Murphy, 48, of Brooklyn Heights, N.Y., one of those standing in line outside Ben's yesterday. "I really feel hopeful about this country for the first time in a long time."

Hope -- and change. Mr. Obama's remarkable candidacy was premised on those themes, which resonated with a nation at war and in the midst of economic crisis.

Today, shortly after taking the oath of office at noon, he will deliver an inaugural address -- probably about 15 to 20 minutes long -- in which he has to explain to the American people how he will deliver on those promises.

Will he find the right words to do that? He'll certainly have a rapt audience. More than 2 million people, Americans from of all ages and backgrounds, are expected to converge on the Mall for today's ceremony. The event will boast not only the tightest security measures ever undertaken to protect a president, but will be freighted with even more symbolism, and irony, than most presidential inaugurations.

The swearing-in will take place on the West Front of a Capitol built by slaves, whose dome is capped by an iron statue called "Freedom" -- cast by a slave.

Mr. Obama will be sworn in with his hand on a bible used by Abraham Lincoln -- the president who ended slavery in the United States -- declaring his full name, Barack Hussein Obama. He will be the first president to use it since Lincoln in 1861.

And he becomes the nation's first black president the day after the national holiday honoring Dr. King's birthday, within sight of the Lincoln Memorial where Dr. King delivered his "I Have a Dream" speech -- and just two weeks before the nation's celebration of the 200th anniversary of Lincoln's birth.

Fairly or not, Mr. Obama's speech is one of the most anticipated in memory -- even after a campaign notable for its stirring oratory.

Mr. Obama wrote the bulk of his inaugural address last weekend, his aides said, and it won't be a laundry list of things to do -- those are better saved for the State of the Union address -- but rather, a forceful call for responsibility and accountability.

The president-elect told ABC News earlier this week that he sees his main task "to try to capture as best I can the moment that we are in ... this is the crossroad that we're at. And then to project confidence that if we take the right measures that we can once again be that country, that beacon for the world."

Since arriving in the nation's capitol two weeks ago, Mr. Obama has made numerous gestures, large and small, designed to reflect his desire for openness and connection, to build bridges, racial, cultural and economic.

There was Friday's visit to Ben's Chili Bowl -- a visit fraught with meaning for the city's black citizens, in a neighborhood rebounding from decades of neglect, in a city still grappling with deeply ingrained poverty, troubled schools and crime. On Saturday night, he took his two daughters to the Lincoln Memorial to show them the inscription from Lincoln's second inaugural address. Tomorrow, 200 ordinary Americans -- the first to respond via e-mail to an online invitation posted on the Obama inaugural Web site -- will be invited into the White House for an open house reception.

Last night, in yet another act of conciliation, Mr. Obama was expected to appear at three "bipartisan dinners" -- for Mr. McCain, Vice President-elect Joseph R. Biden Jr. and former Secretary of State Colin L. Powell. He wouldn't be the only one stepping out. As night fell, street corners began crowding with people in black tie and satin gowns, headed toward hundreds of parties all over this elated, euphoric city.

Some of them brought along pajamas, too -- including Sen. Robert P. Casey Jr., his wife, Therese, and their four daughters, ages 12 to 20, who planned to camp overnight in his office at the Russell Office Building. The family lives in the city's Northwest and worried that morning gridlock would keep them from the big moment, said Kendra Barkoff, Mr. Casey's spokeswoman. Ms. Barkoff will sleep a few blocks away at a friend's house.

"We had to make a decision. When you're five miles from the Capitol and you're worried about traffic, you don't want to risk it," Mr. Casey said. He gathered up four folding cots from Cabella's. Someone will get the office couch for the night.

Today, Mr.. Casey will be seated with the Senate, his wife in the audience and the daughters scattered in other parts of the crowd. Last night he attended the dinner for Mr. Biden while his daughters took in a concert.

"Then, Wednesday, it's back to work," he said.