The Montgomery Bus Boycott was a defining event in the country's history. There had been other attempts to integrate buses (which you can read about in the Wiki essay Events leading up to the bus boycott). However, this one attracted national attention and led to the Supreme Court ruling that the laws behind Montgomery and Alabama's bus segregation were unconstitutional.
According to the National Archives:
Mrs. Parks was not the first person to be prosecuted for violating the segregation laws on the city buses in Montgomery. She was, however, a woman of unchallenged character who was held in high esteem by all those who knew her. At the time of her arrest, Mrs. Parks was active in the local National Association for the Advancement of Colored People (NAACP), serving as secretary to E.D. Nixon, president of the Montgomery chapter. Her arrest became a rallying point around which the African American community organized a bus boycott in protest of the discrimination they had endured for years. Martin Luther King, Jr., the 26-year-old minister of the Dexter Avenue Baptist Church, emerged as a leader during the well-coordinated, peaceful boycott that lasted 381 days and captured the world's attention. It was during the boycott that Reverend Martin Luther King, Jr., first achieved national fame as the public became acquainted with his powerful oratory.WikiWackyWoo picks up the story:
At the time, Parks was secretary of the Montgomery chapter of the NAACP. She had recently attended the Highlander Folk School, a Tennessee center for training activists for workers' rights and racial equality. She acted as a private citizen "tired of giving in". Although widely honored in later years, she also suffered for her act; she was fired from her job as a seamstress in a local department store, and received death threats for years afterwards. Her situation also opened doors.
Shortly after the boycott, she moved to Detroit, where she briefly found similar work. From 1965 to 1988 she served as secretary and receptionist to John Conyers, an African-American U.S. Representative. She was also active in the Black Power movement and the support of political prisoners in the US.
After retirement, Parks wrote her autobiography and lived a largely private life in Detroit. In her final years, she suffered from dementia. Parks received national recognition, including the NAACP's 1979 Spingarn Medal, the Presidential Medal of Freedom, the Congressional Gold Medal, and a posthumous statue in the United States Capitol's National Statuary Hall. Upon her death in 2005, she was the first woman and third non-U.S. government official to lie in honor at the Capitol Rotunda.
Detroit honoured this Civil Rights icon by renaming 12th Street, where the 1967 riot occurred, Rosa Parks Boulevard.