Montgomery, Alabama -- with the boycott of the segregated public bus service in that city. On December 5, 1955, Rosa Parks (a black woman) was arrested for refusing to give up her bus seat to a white person. Parks was a member of the National Association for the Advancement of Colored People (NAACP), and her actions were planned by the NAACP as a way of starting a protest movement against racial segregation. The Montgomery bus boycott lasted until December, 1956, when the Supreme Court upheld a district court's decision that bus segregation is unconstitutional.
It's hard to pinpoint a single beginning point for the civil rights movement. Bear in mind that the landmark Supreme Court decision in Brown v. The Board of Education (1954) had occurred already more than a year before the Montgomery bus boycott began. And pushing for civil rights for black Americans had begun already in the 1940s, following World War II. In 1948, President Harry Truman issued an executive order that ended segregation in the US Armed Services. So the events in Montgomery, Alabama in 1955-1956 were capitalizing on some earlier beginnings that had been made.
