During the War of 1812, he commanded troops which were drafted in Columbia County, and were ordered to the defense of the city of New York.
Van Rensselaer was a member of the New York State Assembly in 1800, 1808, 1808-09, 1811, 1812, 1812-13, 1814, 1814-15 and 1819; and was Speaker in 1812-13.