When Congress passed the Voting Rights Act in 1965, Bennie Thompson was seventeen years old—short of the voting age—so his parents reaped its benefits before he did. The family lived in Bolton, Mississippi, a town of about five hundred people twenty miles west of Jackson. Thompson’s mother, a schoolteacher, and his father, an auto mechanic, had never been able to register and vote.

The VRA essentially put states with histories of racial discrimination into federal receivership to force them to comply with the Fifteenth Amendment’s guarantee that the right to vote could not be denied because of race. As a first step, the federal government sent workers to the South to register Black citizens like Thompson’s parents. To assure further compliance, Section 5 of the act required those states to get approval from the Justice Department or a court before making any changes to their electoral systems.…