Fort Huachuca is a Unite States Army installation under the command of the United States Army Installation Management Command. It is located in Cochise County, in southeast Arizona, about 15 miles north of the border with Mexico. Sierra Vista, which annexed the fort in 1971, is located south and east of the base, and Huachuca City, is to the north and west. Its major tenants are the Army Network Enterprise Technology Command (NETCOM)/9th Army Signal Command and the United States Army Intelligence Center. Libby Army Airfield is located on post and shares the runway with Sierra Vista Municipal Airport; it is on the list of alternate landing locations for the space shuttle, though it has never been used as such.