Humphrey was a delegate to every Republican State convention from 1887 to 1936; and was the commissioner of public lands and buildings of Nebraska from 1891 to 1895. He was president of the Broken Bow board of education from 1898 to 1914. Humphrey was a probate judge from 1906 to 1910, and the mayor of Broken Bow from 1916 to 1917. Humphrey moved to a ranch on the South Loup River in 1920.
Humphrey was elected to the 67th Congress in 1922 to fill the vacancy caused by the death of long-standing representative, Moses Kinkaid. He served until March 3, 1923, not running for reelection.
Humphrey died on a trip to Fort Collins, Colorado in 1937, and is interred in the Broken Bow Cemetery.