The civil rights icon precipitated the 1955 bus boycott in Montgomery, Ala., when on Dec. 1 she refused to give up her bus seat to a white man. Parks, already a member of the NAACP, decided she was tired of giving in to racist laws. She was arrested, and four days later, under the leadership of Martin Luther King Jr., the boycott began. In November 1956, the Supreme Court upheld a lower court's decision that said the segregationist policy was unconstitutional.