Despite the best efforts of local civil rights activists, Mississippi remained virulently committed to segregation in 1964, an unjust practice underscored by the systematic exclusion of African Americans from the political process. In response, Robert Moses of the Student Nonviolent Coordinating Committee developed a campaign to bring a thousand volunteers-primarily enthusiastic young white supporters-to the state to encourage voter registration, provide much-needed education, and convene a more representative delegation to attend the Democratic National Convention. Veteran director Stanley Nelson (Freedom Riders) captures the volatile months of that summer through remarkable period footage and the firsthand testimonies of volunteers who were transformed by their time in Mississippi. With the Supreme Court recently striking down a key section of the Voting Rights Act, Nelson's film is a potent reminder of the sacrifices made half a century ago to ensure civil rights for all and the vigilance needed to protect what they accomplished.