On the evening of December 1, 1955, Rosa Parks, an African American, was arrested for disobeying an Alabama law requiring black passengers to relinquish seats to white passengers when the bus was full. Blacks also were required to sit at the back of the bus. Her arrest sparked a 381-day boycott of the Montgomery bus system and led to a 1956 Supreme Court decision banning segregation on public transportation.
Read more and check out the Guide to Materials for Rosa Parks from the Library of Congress.