On March 7, 1965, hundreds of civil rights activists departed from Selma headed toward Montgomery, Alabama, along US Route 80. The march, part of a larger voting rights movement taking place across the South, was led by twenty-five-year-old John Lewis of the Student Nonviolent Coordinating Committee and Rev. Hosea Williams of the Southern Christian Leadership Conference (SCLC).

Everything went according to plan until the marchers — many of them residents of Selma, joined by clergy, students, and national movement organizers — crossed the Edmund Pettus Bridge, where they encountered a wall of Alabama state troopers on the other side. The police attacked, beating the marchers with nightsticks, firing tear gas, and charging them on horseback during a day of violence later known as Bloody Sunday. The assault was captured on video, and during that evening’s NBC broadcast, confused viewers thought they were watching footage of atrocities in Nazi Germany.

On August 6, in the presence of Lewis, Martin Luther King Jr, and other civil rights leaders, President Lyndon Johnson signed the Voting Rights Act (VRA) of 1965. The law banned tactics long used to suppress black voters, allowed federal monitoring and intervention of elections, and permitted the government to bring lawsuits against states or counties that violated equal ballot access. It also created a preclearance process, in which states with a history of voter discrimination, as judged by a coverage formula, were required to seek preapproval from the attorney general before changing any voting or election procedures.