"Let us not forget as we gather here today that our nation is still at war," President Barack Obama said after laying a wreath at the Tomb of the Unknowns.
"When they give their lives, they are still being laid to rest in cemeteries in quiet corners across our country, including here in Arlington," he said. He told the stories of three soldiers who had died. Each had been devoted to their mission and were praised by others for saving lives.
Earlier in the morning, he and first lady Michelle Obama hosted a breakfast at the White House with "Gold Star" families of service members who have been killed.
Another wreath-laying ceremony was planned at Franklin D. Roosevelt Four Freedoms Park on the southern tip of Roosevelt Island in New York City. The park is a tribute to President Roosevelt's famous speech calling for all people to enjoy freedom of speech, freedom of worship, freedom from want and freedom from fear.
Mayor Michael Bloomberg joined military leaders and others at the Soldiers' and Sailors' Monument in Manhattan. He said celebrate the day and the good weather but also important to "remember the sacrifice that was made so that we could be here."
At the National World War II Museum in New Orleans, about 20 bicyclists clustered around World War II veteran and museum volunteer Tom Blakey, a paratrooper in the 82nd Airborne Division who jumped at Normandy on D-Day -- June 6, 1944 -- and in May 1945 helped liberate the work camp at Wobbelin in northwest Germany.
"Most of us wondered why we were there, killing people and being killed," he said. "We didn't do anything to deserve it. When we got to that camp and saw what was there, the lights came on."
The cycling group makes regular weekend training runs, and on Monday started a Memorial Day ride about seven miles away at the national cemetery in Chalmette, where the Battle of New Orleans -- the last in the War of 1812 -- was fought.
"I'm glad I took this ride to hear a personal story," Scott Gumina, 41, said. "Hearing one man's account of his personal experience was pretty impressive to me."
Across much of New England, several days of heavy rain gave way to sunny skies for parades in towns large and small.
In Portland, Maine, kids and even pets displayed the Stars and Stripes as veterans, youth groups law enforcement officials and civic organizations paraded to Monument Square to the tunes of a marching band, sirens from a police car and the rumble of motorcycles.
"It's a very important day, not only for the Veteran of Foreign Wars but every veteran organization, every branch of the service, and every patriot in general -- every American. This day is hugely significant and should never be forgotten," said David Olson, 66, of Portland, the VFW's state senior vice commander.
He said he was pleased to see a large turnout of youngsters, both in the parade and along the parade route. "As they get older, they'll realize exactly why we do this," he said.
For some veterans, it was a somber event.
Richard Traiser, a Marine injured when his tank came under attack in Vietnam, helped deliver a three-volley salute with the Marine Corps League.
Memorial Day gives those who served an opportunity to get together and remember friends who didn't make it.
"I think about them a lot, especially the people I lost in my platoon," Traiser said. "A couple of kids were 19 years old. I don't dwell on it in a morbid way, but it's on your mind."
In Connecticut, a Waterford man who was killed in the Vietnam War was honored with a hometown park area named for him. Arnold E. Holm Jr., nicknamed "Dusty," was killed when his helicopter was shot down on June 11, 1972. A group of at least 100 dedicated the park this weekend.
In suburban Boston, veterans gathered in a park to mark Memorial Day this year rather than hold a parade because of failing health and dwindling numbers. The city of Beverly called off its parade because so few veterans would be able to march. The parade has been a fixture in the town since the Civil War.
In Atlanta, a dedication of the History Center's redone Veterans Park was scheduled for early evening. Soil from major battlefields will be scattered by veterans around the park's flagpole.
The holiday weekend also marked the traditional start of the U.S. vacation season. AAA, one of the nation's largest leisure travel agencies, expected 31.2 million Americans to hit the road over the weekend, virtually the same number as last year. Gas prices were about the same as last year, up 1 cent to a national average of $3.65 a gallon Friday.
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