Harold David Cunningham was born December 10, 1926 in Arrey, New Mexico. Harold married Cynthia W. on June 7, 1949 and they had three children: Frank W., Catherine S., and Harold D. Jr.

Cunningham enlisted into the United States Army in 1944.

Cunningham graduated from New Mexico State University with a Bachelor of Science degree in 1948.

Cunningham was employed as the president and general manager of Reynolds Electrical & Engineering Co. (REECo) at the Nevada Test Site.