Also known as the Squaw Mountain Gap Filler Annex, the former Baker Gap Filler Annex site was located off of Interstate Highway 15, approximately 24 miles northeast of Baker on Squaw Mountain, San Bernardino County, California. On December 20, 1956, the United States Air Force (USAF) acquired the site from the Department of the Interior Bureau of Land Management (BLM) by letter permit No. LA-1195. The site consisted of 71.6 acres. The site was suppose to fill in gaps in the radar coverage of Kingman Air Force Station in Arizona.
The land for the Baker Gap Filler Annex, (Site Identification Number M-128-F)l was acquired by the Department of the Air Force; however, the requirement for the site was deleted from the Air Defense Command (ADC) Radar Net. No improvements were made to the property.
The U.S. Air Force declared the 71.6-acre site excess on March 28, 1960, because the requirement for the site was deleted from the ADC Radar Net. In a letter dated 28 March 1960 the USAF stated that "pursuant to the provisions of paragraph 9, Air Force Regulation 8704, 28 December 1959, the following described land is hereby declared excess to any further requirements of ADC, effective the date of the letter". The Air Force made no recommendations for retaining, recapture or reuse rights. The USAF recommended that the real property be returned to the Department of Interior. The property was transferred back to BLM public domain on June 2, 1960. The land is presently public domain land managed by BLM.