Glynn was elected as a Democrat to the 56th United States Congress, and served from March 4, 1899, to March 3, 1901. When he took his seat at age 26, Glynn was the youngest member of the House. He was New York State Comptroller from 1907 to 1908, elected in 1906, but defeated for re-election in 1908 by Republican Charles H. Gaus.
