The US Army completed the first transcontinental helicopter flight on August 24, 1956, when an H-21 Shawnee named "Amblin Annie” landed at the Pentagon helipad after a 2,610-mile flight lasting more than 31 hours from San Diego, California. The flight also featured the first ever in-flight refueling of a helicopter.

Originally designed for high-altitude, cold-weather operations, the first H-21s joined the U.S. Air Force in 1953 for rescue operations in the Arctic. Proving to be rugged and reliable, the Shawnee also served in Alaska, Northern Canada and Greenland utilizing wheels, skis, or floats for landing.

It was the first Army helicopter capable of carrying an entire infantry squad. Although the Shawnee usually had a crew of two (pilot and copilot), it could carry either 20 fully-equipped troops or 12 litter patients.

Redesignated CH-21B in 1962, the CH-21 served in Vietnam until 1964, when it was replaced by UH-1 "Huey" and the CH-47 Chinook. The CH-21C version served in combat with the French in Algeria, as well as with the armed forces of Canada, Sweden and West Germany.