Joan R. Kammer Horton grew up in Cincinnati, Ohio, and graduated from Seton High School in 1945. She worked after school for trucking companies and at Kroger’s grocery store. After graduating, she continued to work in the trucking industry and in a bank, and became involved in a competitive rifle club.
In late 1953, Horton joined the Women Marines. After eight weeks of basic training at Parris Island, South Carolina, she was assigned to the Department of the Pacific in San Francisco, California. While there, she ran the rifle range with her future husband, Carl Horton, and worked in an office. Horton was promoted to sergeant on 1 April 1956, and switched to the Reserves in 1957. She and Carl Horton were married in August 1957, and she left the Marine Corps when she became pregnant.
The Hortons lived in Washington State until her husband retired from the Marine Corps in 1969. They moved to Pigeon Key, Florida, where they operated a marine field station for the University of Miami with their three children. They later moved to Davie County, North Carolina, where they briefly ran a shrubbery nursery and then worked in trucking and motel supply. Horton has also volunteered at Veterans Administration hospitals.