Osceola Air Force Station

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Osceola Air Force Station (1951-1975) - A Cold War U.S. Air Force Radar Station. Located near East Farmington, Polk County, Wisconsin. Named Osceola Air Force Station on 1 Dec 1953. Initially assigned a Permanent ID of P-35 and later a Sage ID of Z-35. Deactivated on 31 Mar 1975.


Established in 1950 and became operational on 1 Jan 1951 as East Farmington radar site and renamed Osceola Air Force Station 1 Dec 1953. Manned by the 674th AC&W Squadron whose name was changed on 15 Dec 1959 to the 674th Radar Squadron (SAGE) and again on 1 Feb 1974 to the 674th Radar Squadron.

Initial equipment included two CPS-6B radars. The CPS-6B radars were replaced by one FPS-7 search radar and two FPS-6A height-finder radars in 1959. 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

Osceola SAGE Direction Centers & Sectors
Assigned Direction Center Sector
1 Apr 1951 - 1 Apr 1966 Duluth SAGE Direction Center DC-10 Duluth Air Defense Sector
1 Apr 1966 - 15 Sep 1969 Duluth SAGE Direction Center DC-10 29th Air Division
15 Sep 1969 - 14 Nov 1969 Duluth SAGE Direction Center DC-10 54th Air Division
14 Nov 1969 - 19 Nov 1969 Duluth SAGE Direction Center DC-10 29th Air Division
19 Nov 1969 - 31 Mar 1975 Duluth SAGE Direction Center DC-10 23rd Air Division

The site began operation as a SAGE site on 1 Jul 1959 initially feeding the Duluth SAGE Direction Center DC-10. In 1963 the two FPS-6A height-finders were upgraded to become two FPS-90 height-finders. In the early 1970s the vacuum tube FST-2B was replaced with a solid state FYQ-47 Common Digitizer.


Osceola AFS and the 674th were deactivated on 31 Mar 1975.

Gap Fillers

Osceola AFS was responsible for the maintenance of three remote unattended gap-filler radar sites. The unattended gap filler sites were placed in locations where the main search radar lacked coverage. These sites were equipped with short range FPS-14 or FPS-18 search radars and FST-1 Coordinate Data transmitters that sent digitized radar target data to a SAGE direction center and to the main radar site. Both the radar set and the FST-1 were dual channel to increase site up time. Maintenance teams were dispatched for regularly scheduled maintenance or when fault indicators on the FSW-1 remote monitoring equipment suggested the site had problems. The FSW-1 also allowed remote operation of specific functions such as channel changes for the radar and for the FST-1, it also allowed remote operation of the diesel generators at the gap filler site. The Osceola AFS gap-filler radars were located at Northfield MN, Jim Falls WI and La Crescent MN. Two additional gap-fillers were contemplated but not built.

Osceola AFS Gap Filler Radar Sites (edit list)
ADC NORAD Location State Type From To GPS Notes
P-35B Z-35B Northfield MN FPS-14/FPS-18, FST-1 1957-11 1967-12 44.42064,
Building Exists
Sail on Ground
Tower gone
P-35C Z-35C Jim Falls WI FPS-18, FST-1 1959-07 1968-06 45.03673,
Building in use
Tower in use
P-35F Z-35F La Crescent MN FPS-18, FST-1 1959-11 1967-12 43.85966,
Building exists
Tower gone

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 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. North of the main site was a small 27 unit housing area (originally 9 units) for married personnel.

A separate radio site housed the radio equipment for directing aircraft intercepts. Like most early radar stations, Osceola 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. The Osceola AFS GATR site was located north of the main site.

Osceola AFS Major Equipment List
Search Radar HF Radar Data Systems Radio
Unit Designations
  • 674th Aircraft Control & Warning (AC&W) Squadron (1951-1959)
  • 674th Radar Squadron (SAGE) (1959-1974)
  • 674th Radar Squadron (1974-1975)
674th Assignments

Osceola Air Force Station Partial Commanders List (edit list)
Assumed Relieved Rank Name Cullum Notes
1956 1957 Captain Asmussen, Carl E. N/A
1956 1959 1st Lt. Hobbs, Charles D. N/A
1958 1964 Lt. Colonel Binford, Ed N/A
1967 1968 Lt. Colonel Howard, Jim N/A
1968 Lt. Colonel Scott, Leonard B. N/A
Major Fosgate, Kenneth R. N/A

Note: Reported dates overlap and may be incorrect or reflect periods of intermittant temporary command.

Current Status

Now part of the Association Retreat Center - The ARC.

Location: Near East Farmington in Polk County, Wisconsin. Zoom out to see GATR site location.

Maps & Images

Lat: 45.25139 Long: -92.64278

  • Multi Maps from ACME
  • Maps from Bing
  • Maps from Google
  • Elevation: 1,145'

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 43, 159.
  • 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 169.
  • USGS Geographic Names Information System (GNIS) Database Entry: 2089742


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