Born to a Scots Irish and English father and a Mexican mother, Lansford was raised in a Mexican neighbourhood in East Los Angeles. He had virtually no contact with his father until he was 14. He enlisted in the U.S. Marine Corps in 1940 and served with the 1st Provisional Marine Brigade in Iceland, the 2nd Marine Raider Battalion on Guadalcanal, and Bougainville where he was promoted to sergeant and in the 5th Marine Division on Iwo Jima

Following the war, Lansford attended college under the G.I. Bill and worked as a reporter for the Los Angeles Daily News. During the Korean War he was commissioned as a U.S. Army officer where he became a captain whose duties included being a radio writer with the Armed Forces Radio Service, a Public Information Officer, and a company commander.

Lansford began writing for publications in many American magazines. He wrote several non-fiction books such as the biographies Stranger than Fiction: The Real Life Adventures of Jack London (1958) and Pancho Villa (1965).. The latter was filmed as Villa Rides in 1968 with Lansford doing an early draft of the screenplay.

Lansford wrote many teleplays for American television series such as Four Star Playhouse, Wagon Train,Bonanza, The Rookies, Starsky and Hutch, CHiPs, and The Next Generation. He also wrote the screenplays for made for TV movies depicting Jesse James (The Intruders) and Charles Whitman (The Deadly Tower). He produced, directed, and wrote the film Adios East Los