At the Pentagon in Arlington, Va., thousands of motorcyclists gathered to participate in the 25th "Rolling Thunder" motorcycle rally, May 27, 2012. The event is in its 25th year now. Participants from around the United States gathered at the Pentagon before embarking on a ride around the National Mall in Washington, D.C. This year's Rolling Thunder coincides with the 50th anniversary of the start of the Vietnam War. Many of the participants in the rally are veterans of that war. The rally brings attention to prisoners of war and those missing in action.