On Dec. 5, 1955 the Montgomery Bus Boycott began, one of the most powerful stories of organizing and social change in U.S. history. Yet many people still associate it with an isolated act by Rosa Parks. Out of Montgomery’s 50,000 African American residents, 30,000-40,000 participated in the boycott. For 381 days, they walked, bicycled or car-pooled, depriving the bus company of a substantial portion of its revenue. ©Don Cravens/Time Life/Getty Images.