Materials contain photographs of the HK-1 Hercules, otherwise known as the "Spruce Goose" or the "Flying Boat," from 1942 to 1947. The photographs primarily depict the construction, transportation, and storage of the plane, but also include photographs of the first and only test flight of the HK-1 above Los Angeles Harbor in 1947. Howard Hughes designed the HK-1 as the world's largest plane, capable of transporting large quantities of U.S. military hardware and personnel. In 1947, under the program's new designation H-4 Hercules, Hughes had the plane transported from his factory in Culver City, California to Los Angeles Harbor. On November 2, he piloted the plane during its only test flight. The U.S. Air Force abandoned the controversial project, and Hughes was called to testify before the Truman Committee of the U.S. Senate to justify the use of government funds on a program that never succeeded.

The people associated with Howard Hughes series dates from 1947-1976 and is composed entirely of reference files of newspaper clippings that document Hughes employees, business associates, competitors, and relatives, as well as politicians and government officials that were of interest to Hughes.