David Gilson Mitchell was the son of Richard and Sophia Mitchell, both of revolutionary stock. At age 15, he left his New York home and enlisted in Company C, 111th Pennsylvania Infantry, where he served from 1861 to 1864. After his tour of duty, he reenlisted with Company M, 102nd Pennsylvania Veteran Volunteers and was honorably discharged in 1865. He fought in many iconic Civil War battles including Gettysburg, Cedar Mount, Atlanta, and more than a dozen more.
After the war, he pursued various jobs: the bridge department of the Erie & Pittsburg Railway Company; storekeeping in Rockford, Illinois; farming in Fayette, Iowa; construction for the Chicago, Milwaukee & St. Paul Railway; and operating a steam laundry having returned to Rockford, Illinois. In 1886, he came to California and began ranching in the Perris area.
He was part of Riverside County’s formation when it separated from San Bernardino County in 1893 and was one of the five commissioners appointed by the governor to complete the formation and was selected secretary of the board of supervisors. He was elected county treasurer in the new county’s first elections and continued to be reelected to the post, holding it until his death in 1926. His daughter, Alice Mitchell Tobias, succeeded him in the office.
Mitchell belonged to several fraternal organizations. He was one of the original founding members of Grand Army of the Republic Post 118 and served as post commander in 1899-1900. He was a member of Riverside Lodge #643, Benevolent and Protective Oder of Elks; Knights Templar Commandery, Riverside; Al Malaikah Temple, Los Angeles; and the Junior Order of United American Mechanics where he served as state counselor and state delegate to the national convention in in Detroit in 1910. He was a charter member of the Present Day Club and the Republican Central Committee for Riverside County. He attended the Congregational Church where he was a deacon.