 After returning from the war, Killingsworth went to work as an associate for Long Beach architect Kenneth S. Wing from in 1946-1953.Killingsworth was discovered in 1950 as John Entenza, creator of the Case Study Program, drove by Killingsworth's in-laws' recently built house in Los Alamitos, California.When Entenza found out Killingsworth was the architect, he invited him to participate in the program.