 Sleeper served as a member of the Massachusetts Constitutional Convention of 1853, the Massachusetts Senate, the Massachusetts House of Representatives and, from 1856 to 1858, as the sixth Mayor of Roxbury, Massachusetts.Sleeper was a contestant for the third congressional district of Massachusetts for the election held on November 4, 1862.Although originally ahead in the vote totals, Alexander Rice was later declared the winner by 25 votes (5,045 to 5,020).