The R-4 was the world's first production helicopter and the Air Force's first service helicopter. The original military model, the XR-4, was developed from the famous experimental VS-300 helicopter, invented by Igor Sikorsky and publicly demonstrated in 1940. The XR-4 made its initial flight on January 13, 1942 and as a result of its successful flight tests, the AAF ordered 3 YR-4As and 27 YR-4Bs for service testing and flight training. Of these 30, one went to Burma and one to Alaska, while several others were assigned to the U.S. 

Navy, U.S. Coast Guard and British Royal Navy. They showed such promise that the AAF ordered 100 R-4Bs. The R-4 was first used in combat in May 1944. In a letter to a friend, Col. Philip G. Cochran, Commanding Officer (CO) of the 1st Air Commando Group, wrote "Today the 'egg-beater' went into action and the damn thing acted like it had good sense." The R-4B on display was donated by the University of Illinois in 1967.