Walnut Ridge Air Force Station

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Walnut Ridge Air Force Station (1956-1963) - A Cold War U.S. Air Force Radar Station. Initially assigned a Permanent ID of SM-143 and then a Sage ID of Z-143. Deactivated in 1963.


Established and became operational in 1956 as Walnut Ridge Air Force Station manned by the 725th Aircraft Control and Warning (AC&W) Squadron.

Initial equipment included the MPS-11 search radar a FPS-4 height-finder radar. In 1958 the FPS-4 was replaced by a pair of FPS-6 height-finder radars. This configuration met the requirements for the transition to the SAGE System operation.

SAGE System Transition

The transition of the manual GCI system to the automated SAGE system began with the installation of the FST-2 coordinate data transmitter and search radar upgrades. The FST-2 equipment digitized the radar returns and transmitted the digital returns to the SAGE direction center. Under the SAGE System, interceptor aircraft were directed to their targets by the direction center computers and controllers, greatly reducing the need for local controllers and equipment at every radar station.

The FST-2 was a very large digital system using vacuum tube technology. Over 6900 vacuum tubes were used in each FST-2 requiring 21 air-conditioned cabinets, 40 tons of air conditioning, 43.5 kva of prime power, and usually a large new addition to the operations building. The FST-2B modification added two more cabinets but with newer solid-state (transistor) technology to process coded responses from aircraft transponders.

SAGE System Operation

Walnut Ridge SAGE Direction Centers & Sectors
Assigned Direction Center Sector
1 Jul 1961 - 1 Aug 1963 Truax SAGE Direction Center DC-07 Chicago Air Defense Sector

The site began operation as a SAGE site in 1961 initially feeding the Truax SAGE Direction Center DC-07.


Walnut Ridge AFS and the 725th were deactivated on 1 Aug 1963.

Physical Plant

The physical plant of the site was divided into the main site, a cantonment area, a housing area, and a radio site. The main site was known locally as the "A" area and housed the operations buildings, the radar towers, and the backup generators. The cantonment area housed the enlisted barracks, the bachelor officer's quarters, the orderly room, the dining hall, the motor pool, and other support buildings. Many of these buildings were Quonset type buildings and the area was known as the "B" area. Apart from the main site was a small 27 unit housing area for married personnel.

A separate radio site housed the radio equipment for directing aircraft intercepts. Like most early radar stations, Walnut Ridge originally had a radio transmitter site and a separate radio receiver site used by local controllers for voice direction of fighter interceptors to their targets. With the SAGE System, the SAGE Direction centers had the primary task of directing intercepts and the local radio sites were reconfigured, usually into a single site that was known as the Ground to Air Transmitter Receiver (GATR) site. The GATR site communicated with the interceptors from either the local site or the SAGE direction center via voice commands and/or a digital data link.

Walnut Ridge AFS Major Equipment List
Search Radar HF Radar Data Systems Radio
Unit Designations
  • 725th Aircraft Control & Warning (AC&W) Squadron (1956-1962)
  • 725th Radar Squadron (SAGE) (1962-1963)
725th Assignments
  • 8 Apr 1955 - Activated at Tinker AFB, OK, assigned to 33rd AD.
  • 1 Mar 1956 - Transferred to 20th AD.
  • Early Jul 1956 - Moved to Walnut Ridge AFS, AR.
  • 1 Jan 1960 - Transferred to Kansas City ADS.
  • 1 Jul 1961 - Transferred to Chicago ADS.
  • 1 May 1962 - Redesignated from AC&W Sq to 725th Radar Sq (SAGE).
  • 1 Aug 1963 - Discontinued.

Current Status

Various buildings from the cantonment area are still in use by Williams Baptist College, Frolic Footwear Company, and the Municipal Airport. The main site appears to be in use by the V & B Manufacturing Company. The housing area is now private homes.

Location: Walnut Ridge in Lawrence County, Arkansas.

Maps & Images

Lat: 36.13 Long: -90.91917

  • Multi Maps from ACME
  • Maps from Bing
  • Maps from Google
  • Elevation: 272'

See Also:


  • Cornett, Lloyd H. & Johnson, Mildred W., A Handbook of Aerospace Defense Organization (1946-1980), Office of History ADC, Peterson AFB, Colorado, 31 Dec 1980, 179 pages, Pdf, page 162.
  • Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf, page 98.


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