In 1960, Boeing bought Vertol, a helicopter manufacturer in Philadelphia, Pa. The company had three tandem-rotor helicopters under production: the Chinook for the Army, the Sea Knight for the Navy and the Marines, and the commercial 107-II for the airlines.
The twin-turbine tandem-rotor CH-46A Sea Knight won a design competition for a medium assault transport helicopter for the Marine Corps in 1961 and made its first flight in August 1962.

The first U.S. Marine Corps Sea Knight was delivered in 1964 and began military service during the Vietnam War a year later, carrying troops and cargo to and from Navy ships in the China Sea.

Between 1964 and 1990, Boeing Vertol delivered over 600 Sea Knights. The U.S. Marine Corps retired the CH-46 Sea Knight in August 2015.