In March 1955, Claudette Colvin—a fifteen-year-old black schoolgirl in Montgomery—refused to give up her bus seat to a white man in violation of Jim Crow laws, local laws in the Southern United States that enforced racial segregation. King was on the committee from the Birmingham African-American community that looked into the case; E. D. Nixon and Clifford Durr decided to wait for a better case to pursue because the incident involved a minor.
Nine months later on December 1, 1955, a similar incident occurred when Rosa Parks was arrested for refusing to give up her seat on a city bus. The two incidents led to the Montgomery bus boycott, which was urged and planned by Nixon and led by King. The boycott lasted for 385 days, and the situation became so tense that King's house was bombed. King was arrested during this campaign, which concluded with a United States District Court ruling in Browder v. Gayle that ended racial segregation on all Montgomery public buses. King's role in the bus boycott transformed him into a national figure and the best-known spokesman of the civil rights movement.