Hidden Hills Lake Test Annex was used by Edwards AFB as an emergency landing field and aborted mission area in conjunction with a continuous tracking radar range. The radar range was capable of tracking the X-15 research aircraft and obtaining a real time evaluation of various parameters as they occurred in the aircraft. No permanent structures were built on the site; all facilities used at the site were portable.
The 2,480 acres of Hidden Hills Lake Test Annex were retransferred to the U.S. Department of the Interior on 8 February 1971, pursuant to the date specified in Special Land Use Permit LA-0168990. A notice of cancellation of lease was given to the U.S. Department of the Interior on 12 March 1971, indicating the Department of the Air Force exercises its rights reserved in said permit and will quit, relinquish, and give up said premises on 8 February 1971. Currently, the site is controlled by the U.S. Department of the Interior, Bureau of Land Management (BLM). The site is undeveloped desert land with most of the site located on a dry lake bed. No USAF improvements were observed on the site.
