Rolling Thunder is a United States advocacy group that seeks to bring full accountability for prisoners of war(POWs) and missing in action (MIA) service members of all U.S. wars. The group's first demonstration was in 1988. It was incorporated in 1995, and has more than 90 chapters throughout the US, as well as overseas.
Their main annual event occurs on the Sunday before Memorial Day, in which members make a slow ride on a dedicated, closed off, pre-set route, called Ride to the Wall in Washington D.C., referring to the Vietnam Veterans Memorial Wall, also called the Ride for Freedom, which leaves the Pentagon parking lot at noon, crosses the Memorial Bridge, and ends at the Vietnam Veterans Memorial. During the Rolling Thunder weekend, members and supporters spend time at the Thunder Alley (the official vendor site for the event), visit significant areas of Washington D.C., particularly the numerous memorials, and hear speeches given by members, supporters, military officials and politicians.
info courtesty of: wikipedia