Born in Illinois and raised in Iowa, Mills went to the Arizona Territory and applied his engineering education in the mining industry.
[2] Mills returned to Arizona and joined the Detroit Copper Mining Company at Morenci as its general manager.
At the outbreak of the Spanish American War, he resigned from the company to join Teddy Roosevelt's Rough Riders as a private.
[1] When the United States entered World War I, Mills volunteered to work at the US Army Aircraft Department.
He organized the Apache Powder Company in rural Cochise County as a cooperative venture of the large mines in the state.
[1] Mills died January 17, 1929, at St. Joseph's Hospital in Phoenix and was buried in Forest Lawn Cemetery, in Los Angeles, California.