He married Margaret Asbreen Mitchell on February 19, 1872, and they had eleven children, Agnes Elmer, Mary Magadelene, Rufus Omar, Anna Ida, Florence Palestine, Alvin Kenneth, Lillie Effie, Orville Palmer, Lacey Edith, Eunice Minnie, and Eris Carleton.

[1] Entering the ministry in the Methodist Episcopal Church in 1880, Callahan continued to engage in agricultural pursuits, sawmilling, and mining.

[2] In 1896, Callahan was nominated for Congressional delegate from Oklahoma Territory, and was elected by a plurality of less than fifteen hundred, running on the Free Silver ticket to the 55th United States Congress.

After leaving politics, Callahan relocated to Enid, Garfield County, Oklahoma, where he published the Jacksonian until January 1, 1913.

Callahan resided in Enid, Oklahoma until his death there on May 3, 1935 (age 82 years, 135 days).