“Through their defiant journeys, the Freedom Riders sent a resounding message to the rest of our nation that desegregation was a moral imperative,” President Obama said yesterday in his proclamation honoring the 50th anniversary of the Freedom Ride.

Fifty years ago today, activists from different races stepped foot on buses headed to the segregated south with one goal in mind: freedom. The two buses leaving Washington D.C. on May 4, 1961, carried 13 passengers—seven black and six white—determined to make it to New Orleans. They traveled through Richmond, Virginia, Greensboro, North Carolina, and Rock Hill, South Carolina. It was there, in Rock Hill, where Georgia Rep. John Lewis was attacked for attempting to enter a white-only bus terminal waiting room. Additionally, 10 days into the trip, the Freedom Riders’ Greyhound bus was bombed in Anniston, Alabama, by the Ku Klux Klan. Furthermore, many were beaten in Birmingham, Alabama, only blocks from the Sheriff’s home.

The activists were not deterred by the violence. Over the next year, more that 436 people on 60 freedom buses traveled to the south to agitate for change. In November 1961, an Interstate Commerce Commission ruling that segregation on interstate buses and facilities was illegal, took effect.

This month, PBS will debut a documentary on the movement, as students retrace the journey of the Freedom Riders.