He served two terms as the State's Attorney for Jackson County, once from 1906 to 1908 and again from 1916 to 1920.

[2][3] In 1928, when Frank L. Smith resigned the U.S. Senate seat he had won in 1926, after twice having his credentials refused by the Senate, Glenn defeated future Chicago mayor and Democrat Anton Cermak in a special election, 54.5 to 44.9 percent respectively, to serve out Smith's term.

[2] When Glenn ran for re-election in 1932, he was defeated by Democrat William H. Dieterich, 46.0 to 52.2 percent respectively.

[4] Glenn ran, unsuccessfully, in 1936 as well, being defeated by Democratic incumbent J. Hamilton Lewis, 40.7 to 56.5 percent respectively.

[3] Glenn died on March 11, 1959, at Portage Point in Onekama Township, Michigan.