Barack Obama, The Inauguration

OBAMA FOR USA. Mr. Obama took the oath of office on the west front of the U.S. Capitol, where slaves had once baked the bricks, sawed the timber and laid the stone for the foundation. He rose to speak a few minutes after noon, looking out at an ocean of hope, close to two million people gathered on the National Mall, once a slave market, all the way to the Lincoln Memorial, honoring the president who freed the slaves.

The ceremony began with a prayer form the Rev. Rick Warren, a conservative minister selected by Mr. Obama to give the invocation despite protests from liberals and gay activists. He told the crowd: "We know today that Dr. King and a great cloud of witnesses are shouting in heaven."

Chief Justice John G. Roberts Jr., 53, rose to do the swearing-in. For a couple of smooth-talking constitutional experts, Justice Roberts and Mr. Obama had a hard time getting through the constitutional oath of office, with Justice Roberts stumbling over where to place "faithfully'' in "I will faithfully execute the office of the president of the United States.'' (The two did a do-over on Mr. Obama's first day in office, to put to rest any doubts as to whether he had been properly sworn in.)

In his 18-minute inaugural address, the new president left it to others to explicitly mark the history, making only passing reference to his own barrier-breaking role, that " a man whose father less than 60 years ago might not have been served at a local restaurant can now stand before you to take a most sacred oath."

The somber, muscular tone of the inaugural address surprised some who expected the more soaring rhetoric of the campaign. But this was the speech of a new president completely aware of the crisis confronting him. Even as he began speaking, the Dow Jones average was sinking on another day of huge bank losses.

Mr. Obama continued the modern custom of thanking his predecessor, but at several points he bluntly suggested that his predecessor had left things in a shambles. He tied America's economic peril to an era "of greed and irresponsibility on the part of some, but also our collective failure to make hard choices and prepare the nation for a new age."

Mr. Obama tempered the day's celebration with a sober assessment of the state of the economy, noting the spate of home foreclosures, shuttered businesses, lost jobs, costly health care, failing schools, energy dependence and the threat of climate change.

"Less measurable but no less profound is a sapping of confidence across our land, a nagging fear that America's decline is inevitable, that the next generation must lower its sights," he said. "Today, I say to you that the challenges we face are real. They are serious and they are many. They will not be met easily or in a short span of time. But know this, America, they will be met."

When the new president turned to foreign policy, he had more implicit criticisms, noting that the Cold War was won "not just with missiles and tanks," but by leaders who understood "that our power alone cannot protect us, nor does it entitle us to do as we please." It grows instead, he said, "through its prudent use."

It was a message much of the world was waiting to hear. But it was matched with a warning to America's enemies, especially terrorists and terror-sponsoring nations, that "you cannot outlast us, and we will defeat you." The new president declared that it's time to "begin again the work of remaking America" and "we are ready to lead once more."

On the streets of Washington, strangers hugged one another. Many could no longer feel their feet from standing in the cold, but there was joyful dancing anyway.

The Obamas attended 10 of the inaugural balls, going first to the D.C. Neighborhood Inaugural Ball, a symbolic choice given the first couple's pledge to involve themselves in the fabric of the city, rather than living their lives in the predominantly white Oz of the Washington political elite. For their first dance, Beyoncé sang "At Last." At the Commander-in-Chief Ball, the new president chatted via satellite with a military team from Illinois serving in Afghanistan. At one of their stops, he asked the crowd, "First of all, how good-looking is my wife?"

His next date, the one with the Oval Office, would arrive in a few hours.

The portions of this article leading up to President Obama's inauguration were adapted from "OBAMA: The Historic Journey," which was written by Jill Abramson, the managing editor of The New York Times in collaboration with the reporters and editors of the Times who covered Mr. Obama's campaign. The book was published by The New York Times and Callaway.