President Barack Obama is among the Americans observing Memorial Day, a national holiday to honor those who have died in military service to the country.
The president will lay a wreath at the Tomb of the Unknowns at Arlington National Military Cemetery just outside Washington, D.C. The cemetery holds the remains of more than 300,000 people, including veterans from all the nation's wars.
Parades, ceremonies and other special events are being held across the United States. The Department of Veterans Affairs said nearly one-million American men and women have died in military service to the country.
Memorial Day also is the unofficial start of the summer season, and many Americans will spend the day enjoying barbecues and other outdoor activities.
On Sunday, thousands of motorcycle riders from around the country rallied in Washington for their annual tribute to military veterans. The "Rolling Thunder" participants gathered to draw attention to the cases of missing U.S. military personnel and for veterans' causes.
The motorcyclists rode from the Pentagon in Arlington into Washington, where they passed the Vietnam Veterans Memorial as they circled the National Mall.