 In 1912, Mapes defeated incumbent Democratic U.S. Representative Edwin F. Sweet to be elected as a Republican from Michigan's 5th congressional district to the 63rd United States Congress.He was re-elected to the thirteen succeeding Congresses, serving from March 4, 1913, until his death in New Orleans, Louisiana on December 12, 1939.During the 66th Congress, he served as chairman of the Committee on the District of Columbia.