Lamar returned to the United States House of Representatives in 1873, becoming the first Mississippi Democrat elected to the House since the end of the Civil War. He remained in the House until 1877, and represented Mississippi in the Senate from 1877 to 1885. He opposed Reconstruction and voting rights for African Americans. In 1885, he accepted appointment as Grover Cleveland's Secretary of the Interior. In 1888, the Senate confirmed Lamar's nomination to the Supreme Court, making Lamar the first Southerner appointed to the court since the Civil War. He remained on the court until his death in 1893.