American flags, patriotic songs and chants of "U-S-A!" filled the air in Mashpee, down the road from a military reservation that is home to Air National Guard troops deployed to Iraq.
"This is not a war of conquest, it is a war of liberation," retired U.S. Navy Capt. Thomas Hudner told the crowd of about 2,000.
About 60 miles north at Boston Common, a police-estimated crowd of 25,000 protested the war. Nuns, veterans and students listened to speakers and musical acts before marching to Boylston Street for a "die in," during which they collapsed on the streets to dramatize war deaths.
Eric Weltman, one of the protest organizers, said it was intended to show opposition not only to the Iraq war but to potential U.S. military action elsewhere.
"We're working now to stop the next invasion," Weltman said. "We've invaded Afghanistan and Iraq. Who's next? Iran? North Korea? Colombia?"
In Harrisburg, Pa., the steps of the state Capitol were packed with flag-waving war supporters. Police said about 8,000 people showed up, while organizers put the number at 12,000.
"I knew that today we would show where America is at on this issue," organizer and radio talk show host R.J. Harris said. The 48-year-old noted that an anti-war demonstration at the same site a week ago drew about 100 people.
In Miami's Little Havana, about 3,000 Cuban exiles and other Latin Americans chanted "Bush, Bush, Bush" as lawmakers voiced support for the war opposition to Cuban leader Fidel Castro.
In San Francisco, a few hundred war supporters observed a moment of silence to honor those troops who have already died. And in South Central Los Angeles, which has seen several shootings in recent days, hundreds of anti-war demonstrators gathered to protest the violence abroad and to remind the world of the violence they suffer at home.
"Leave those Iraqis alone and come over and take care of business here first," Linda Bolton, 48, said. "Clean up here first before you clean up someone else's home."
Other demonstrations drew hundreds of war opponents to New York City's Times Square, Denver, and Paterson, N.J.
War supporters gathered in Jacksonville, Fla., Honolulu, Cleveland and near Fort Campbell, Ky., and Fort Stewart, Ga., where some of the troops killed or missing were stationed.
Hundreds of people in Mission, Texas, hometown of prisoner of war Army Spc. Edgar Hernandez, prayed at a downtown rally for the safe return of him and other troops.
"We have prayed to avoid this war, and it was not to be," the Rev. Roy Snipes, a Roman Catholic priest, said at the Mission rally. "We pray now for our soldiers to be noble, valiant and victorious."
Throughout the world, anti-war demonstrators turned out in the thousands Saturday from South Korea to Chile, spattering streets with paint and jeering outside U.S. embassies. More than 100,000 people protested in strongly anti-war Germany, half of them at a rally in Berlin.