Rolling Thunder in Washington (12 images)

Bikers drive by the Lincoln Memorial during XXI Rolling Thunder on May 25, 2008 in Washington. Thousands of bikers descended on Washington for the traditional Memorial Day weekend ride through the nation's capital. (UPI Photo/Kamenko Pajic)

An unidentified member of the U.S. Marine Corps salutes bikers taking part in XXI Rolling Thunder at Lincoln Memorial on May 25, 2008 in Washington. Bikers from across US descended on Washington for the traditional Memorial Day weekend ride through the nation's capital. (UPI Photo/Kamenko Pajic)

President George W. Bush (R) receives membership in and a vest and hat from Sgt. Arthur "Artie" Muller, the founder and national director of Rolling Thunder, as President Bush arrives on the South Lawn of the White House on May 25, 2008. (UPI Photo/Dennis Brack/Pool)

Motorcyclists ride by the Lincoln Memorial during Memorial Day weekend in Washington on May 24, 2008. Members of the Rolling Thunder organization, a veterans advocacy organization that works for the return of prisoners of war and missing in action from all of the conflicts of the United States, annually visits Washington D.C. during Memorial Day weekend. (UPI Photo/Alexis C. Glenn)