Civil rights activists known as Freedom Riders sit at a bus station in Birmingham, Alabama, in May 1961. That month, the Freedom Ride movement began with interstate buses driving into the Deep South to challenge segregation that persisted despite recent Supreme Court rulings. In some cities, the activists were arrested and brutally beaten. Donald Uhrbrock/The LIFE Images Collection/Getty Images
Two leaders of the civil rights movement -- the Rev. Ralph Abernathy, left, and the Rev. Martin Luther King Jr. -- wait for news about Freedom Riders. There were at least 60 Freedom Rides from May until December of 1961. Paul Schutzer/The LIFE Picture Collection/Getty Images
A white man in Anniston, Alabama, sits in front of a bus to prevent it from leaving the station with a load of Freedom Riders on May 15, 1961. AP
Freedom Riders sit outside a bus after it was set on fire by a white mob in Anniston on May 14, 1961. Bettmann Archive/Getty Images
National Guardsmen and U.S. marshals from Mississippi are seen through a bus window as Freedom Riders travel from Montgomery, Alabama, to Jackson, Mississippi. Lee Lockwood/The LIFE Images Collection/Getty Images
A group of Freedom Riders from Nashville, Tennessee, are arrested after arriving in Birmingham. Bull Connor, the Birmingham police commissioner, said the group was being arrested for its own protection. AP
John Lewis, left, and James Zwerg stand together after being attacked and beaten by segregationists in Montgomery, Alabama, on May 20, 1961. Lewis is now a U.S. congressman from Georgia. Zwerg tells the story behind the photo Bettmann Archive/Getty Images Freedom Riders endure tear gas that was thrown into Abernathy's church in Montgomery on May 21, 1961. A. Y. Owen/The LIFE Images Collection/Getty Images
The National Guard takes people to safety after Abernathy's church was hit with tear gas bombs. Paul Schutzer/The LIFE Picture Collection/Getty Images
Lewis, with his head bandaged, relaxes with fellow Freedom Riders at a safe house in Montgomery. Paul Schutzer/The LIFE Picture Collection/Getty Images
In addition to segregation on buses and trains, there were also segregated waiting rooms at transit stations. Paul Schutzer/The LIFE Picture Collection/Getty Images
Freedom Riders look out from bus windows during a stop. Paul Schutzer/The LIFE Picture Collection/Getty Images
A Freedom Rider and a National Guardsman sleep on a bus ride from Selma, Alabama, to Montgomery. Bruce Davidson/Magnum Photos