seminal event in the U.S. Civil Rights Movement, was a political and social protest campaign against the policy of racial segregation on the public transit system of Montgomery, Alabama. The campaign lasted from December 1, 1955—when Rosa Parks, an African American woman, was arrested for refusing to surrender her seat to a white person—to December 20, 1956, when a federal ruling, Browder v. Gayle, took effect, and led to a United States Supreme Court decision that declared the Alabama and Montgomery laws requiring segregated buses to be unconstitutional. an associated network of white supremacist organizations in the United States, concentrated in the South. The first was formed on July 11, 1954 After 1956, it was known as the Citizens' Councils of America. With about 60,000 members across the United States, mostly in the South, the groups were founded primarily to oppose racial integration of schools, but they also supported segregation of public facilities during the 1950s and 1960s. Members used severe intimidation tactics including economic boycotts, firing people from jobs, propaganda, and occasionally violence against civil-rights activists.