The surging crowd, shouting "Bush out now" and "Peace now," marched in front of the White House and then to the Washington Monument in an 11-hour marathon of dissent.
They were young people with green hair, nuns whose anti-war activism dates to Vietnam, parents mourning their children in uniform killed in Iraq, and uncountable families motivated for the first time to protest.
President George Bush himself was out of town, monitoring hurricane recovery efforts from Colorado and Texas. The protesters shouted for his impeachment.
"We have to get involved," said Erika McCroskey, 27, who came with her younger sister and mother for her first demonstration, traveling in just one of the buses that poured into the capital from far-flung places.
"Bush Lied, Thousands Died," said one sign. "End the Occupation," said another.
Police Chief Charles Ramsey, noting that organizers had hoped to draw 100,000 people, said, "I think they probably hit that."
A few hundred people in a counter-demonstration in support of Bush's Iraq policy lined the protest route near the FBI building. The two groups shouted at each other, a police line keeping them apart.
Ramsey said the day's protest unfolded peacefully under the heavy police presence. "They're vocal but not violent," he said.
While united against the war, political beliefs varied. Paul Rutherford, 60, said he is a Republican who supported Bush in the last election and still does, except for the war.
"President Bush needs to admit he made a mistake in the war and bring the troops home, and let's move on," Rutherford said. His wife, Judy, 58, called the removal of Saddam Hussein "a noble mission" but said U.S. troops should have left when claims that Iraq possessed weapons of mass destruction proved unfounded.
"We found that there were none and yet we still stay there and innocent people are dying daily," she said.
Arthur Pollock, 47, said he was against the war from the beginning. He wants the soldiers out, but not all at once.
"They've got to leave slowly," said Pollock, attending his first protest. "It will be utter chaos in that country if we pull them out all at once."
From the stage, though, the speeches were hard-edged and critical of Bush on far more fronts than Iraq. Groups representing a bazaar of causes attacked administration policies on the poor, on hurricane response, on the Cuban embargo and much more.
The protest in the capital showcased a series of demonstrations in foreign and other U.S. cities. A crowd in London, estimated by police at 10,000, marched in support of withdrawing British troops from Iraq. Highlighting the need to get out, protesters said, were violent clashes between insurgents and British troops in the southern Iraq city of Basra.
In Rome, dozens of protesters held up banners and peace flags outside the U.S. Embassy and covered a sidewalk with messages and flowers in honor of those killed in Iraq.
Cindy Sheehan, the California mother who drew thousands of demonstrators to her 26-day vigil outside Bush's Texas ranch last month, won a roar of approval when she took the stage before the Washington march. Her 24-year-old son, Casey, was killed in Iraq last year.
"Shame on you," Sheehan admonished, directing that portion of her remarks to members of Congress who backed Bush on the war. "How many more of other people's children are you willing to sacrifice?
She led the crowd in chanting, "Not one more."
Separately, hundreds of opponents of the World Bank and International Monetary Fund danced to the beat of drums in the Dupont Circle part of the city before marching toward the White House to join the anti-war protesters.
"Probably the justification offered for most wars is tied in with economics," said Jack Brady, 57, attending the anti-IMF protest. "And the losers are the people, for the most part."
Supporters of Bush's policy in Iraq assembled in smaller numbers to get their voice heard in the day's anti-war din. About 150 of them rallied at the U.S. Navy Memorial.
Gary Qualls, 48, whose Marine reservist son, Louis, died last year in the insurgent stronghold of Fallujah, asked: "If you bring them home now, who's going to be responsible for all the atrocities that are fixing to happen over there? Cindy Sheehan?"