In Chicago about 5,000 protestors gathered at Union Park and marched to Federal Plaza. Three students were arrested for walking on the street and charged with disobeying a police officer, resisting arrest, and damaging to property, reports CBS News affiliate WBBM in Chicago.
In Seattle, thousands of marchers were led by a small group of Iraq war veterans.
At Occidental Park, where the protesters rallied after the march, the American Friends Service Committee displayed scores of combat boots, one pair for each U.S. solider killed in Iraq.
Rain dampened the New York City march, but thousands of raincoat-wearing protestors still showed up. Among the throngs marching down Broadway was a man carrying cardboard peace doves. Some others dressed as prisoners, wearing the bright orange garb of Guantanamo Bay inmates and pushing a person in a cage.
In San Francisco, it also rained, but at least 10,000 people participated. Organizers of the event estimated about 30,000 people showed up.
"I got the sense that many people were at a demonstration for the first time," said Sarah Sloan, one of the event's organizers. "That's something that's really changed. People have realized the right thing to do is to take to the streets."
In the shadow of the National Constitution Center and Independence Hall in Philadelphia, a few hundred protesters ranging from grade school-aged children to senior citizens called on President Bush to end funding for the war and bring troops home.
Marchers who braved severe wet weather during the walk of more than 30 blocks were met by people lining the sidewalks and clutching a long yellow ribbon over the final blocks before Independence Mall. There, the rally opened with songs and prayers by descendants of Lenape Indians.
"Our signs are limp from the rain and the ground is soggy, but out spirits are high," said Bal Pinguel, of the American Friends Service Committee, one of the national sponsors of the event. "The high price we are paying is the more than 3,800 troops who have been killed in the war in Iraq."
Vince Robbins, 51, of Mount Holly, N.J., said there needed to be more rallies and more outrage.
"Where's the outcry? Where's the horror that almost 4,000 Americans have died in a foreign country that we invaded?" Robbins said. "I'm almost as angry at the American people as I am the president. I think Americans have become apathetic and placid about the whole thing."
Protests were also held in Boston, New Orleans, Los Angeles, Salt Lake City, Orlando, Fla., and Jonesborough, Tenn.