Reynolds v. Sims, 377 U.S. 533 (1964) was a United States Supreme Court case that ruled that state legislature districts had to be roughly equal in population. The case was brought on behalf of voters in Alabama, but the decision affected both northern and southern states that had similarly failed to reapportion their legislatures in keeping with changes in state population after its application in five companion cases in Colorado, New York, Maryland, Virginia, and Delaware.