Several thousand people marched along Pennsylvania Avenue from the Washington Monument to the Capitol, many carrying signs reading "Congress You're Fired" and "Let Failures Fail and "Impeach Obama."
"It wouldn't bother me to make a clean sweep," said Michael Power of Decatur, Ala., endorsing term limits for members of Congress. "There are some good ones, but we can lose those."
In Sacramento, an estimated 4,000 people poured into the former McClellan Air Force Base site for the "United to the Finish" rally - far fewer than the 25,000 to 50,000 crowd organizers had predicted.
Leslie and Gary Morrison of Redding drove 150 south to Sacramento with their dog Phoebe, just two weeks after flying to Washington to attend a large rally hosted by conservative commentator Glenn Beck. They said they liked the feeling of solidarity at the tea party events.
"This is a way to get people focused before the election," Leslie Morrison said. "And it's a way to get the tea party's true numbers seen."
Many attending rallies in Washington, Sacramento and St. Louis wore red, white and blue clothing and carried yellow flags with the picture of a snake coiled above the inscription "Don't Tread On Me."
In St. Louis, they packed the area between the Gateway Arch and the Mississippi River, and vendors sold lemonade, meat on sticks, T-shirts and other souvenirs. A band dressed in powdered wigs and 18th century clothing, belted out KISS's "I Want to Rock 'N Roll All Night."
Mary Jane Corcoran, 58, who works in medical administration, made the 360-mile trip from Dayton, Ohio.
"When you're used to your local tea party with 40 people, it's nice to get together with a lot of people that feel the way you do," Corcoran said. "This is like a shot in the arm to get us going for the November election."
Organizers say the events intended to call attention to what they describe as big government run amok and to recall the sense of national unity Americans felt the day after the attacks of Sept. 11, 2001.
The rallies also represent an opportunity to build momentum before the November election. The tea party is counting on its members to turn out in large numbers and prove that the movement is a political force with staying power.
"We've lost respect in the world. We are going broke. The American dream is dying and our social and cultural fabric is unraveling," said Rep. Mike Pence, R-Ind., who spoke at the Washington rally. "People are scared. If we do not succeed in November, all that once was good and great about this country could someday be gone."
Most of the rally-goers were already faithful tea party activists, and it will take a lot more than just them to make real waves at the polls, acknowledged a co-founder of the nationwide Tea Party Patriots group, which organized Sunday's events.
"We want to fire people up today, so that then they'll go out and get the new people," Mark Meckler of Nevada City, Calif., said backstage at the Sacramento event.
Tea Party Patriots claims to be the nation's largest tea party group, with 2,700 chapters, including at least 175 in California.
Beck and another tea party favorite, former Alaska Gov. Sarah Palin, spoke to a crowd in Anchorage, Alaska, late Saturday - the ninth anniversary of the terrorist attacks - and discussed their feelings about that day in 2001.
"Here we are so many years later, and I fear we are forgetting," Beck said.
Party activists reject characterizations of their movement as an extension of the GOP, but the vast majority of its members are Republicans and independents who vote Republican.
But not Corcoran, who went to the St. Louis rally to show her opposition to big government.
"I've sort of gotten away from being a Republican or a Democrat," she said. "I'm just a conservative."
Freking reported from Washington, D.C. Associated Press Writer Jim Salter in St. Louis also contributed reporting.