Cavalier Air Force Station is a United States Air Force installation in Pembina County, North Dakota, home to the 10th Space Warning Squadron of the 21st Space Wing based at Peterson Air Force Base in Colorado. The station is located approximately 5 km north and 3 km west of Mountain, about 20 km from Cavalier. The facility was built as a part of the Stanley R. Mickelsen Safeguard Complex supporting the U.S. Army's Safeguard anti-ballistic missile program. The Safeguard program was deactivated in 1976, and the site handed to the Air Force.