Duluth SAGE Direction Center DC-10

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Duluth SAGE Direction Center DC-10 (1959-1983) - A Cold War SAGE System Direction Center first established in 1959 on Duluth Airport, Duluth, Saint Louis County, Minnesota. Named Duluth SAGE Direction Center after the location. Assigned a Sage ID of DC-10. Deactivated as a SAGE Direction Center in 1983.

History of Duluth SAGE Direction Center

Construction began on 2 May 1956, the building was accepted on 20 Nov 1957 and the direction center became operational on 15 Nov 1959 as Duluth SAGE Direction Center DC-10.

SAGE System Data Flow

Direction center equipment included the duplex FSQ-7 computer system and associated communication equipment. The FSQ-7 computer system assembled digitized inputs from USAF Radar Sites to provide tracking and identification of all aircraft within their sector of responsibility. The digitized radar inputs came from USAF Radar Sites, airborne radar pickets, Texas Towers, Gap Filler Radar Sites and other radar sources. The total picture of aircraft in the sector was assembled and any unknown aircraft were checked out and hostile aircraft were engaged by USAF fighter aircraft, Bomarc missiles or NIKE missiles. The primary defense was against the Soviet threat of a mass nuclear bomber attack on the US. The system evolved before the advent of ICBMs and provided no missile defense against them.

The computer technology was first generation vacuum tube equipment and required significant power and air conditioning. The physical plant of the direction center was enclosed in a large multi-story concrete blockhouse that housed the duplex FSQ-7 computer, communications equipment, a powerhouse, air conditioning systems and operational areas. The operational areas included radar mapping, air surveillance, identification, communications and weapons direction.

The enormous cost of the radar sites, direction centers, personnel, and training caused an immediate reevaluation and almost as quickly as they were built some facilities were closed. The first mass closures began in the 1960s when many radar sites and virtually all the gap filler sites were closed. The first round of direction center closures came in 1963 when six were closed, a second round in 1966 and a third in 1969 that closed a total of 17 out of 23. The remaining six direction centers became SAGE Regional Control Centers (RCCs) still using the massive FSQ-7 vacuum tube computers. As the direction centers and radar sites closed the remaining sites were realigned into ever-increasing sectors.

A new Joint Surveillance System (JSS) evolved as a partnership between the Air Force and the FAA to provide nationwide radar coverage. When completed in 1983 it consisted of only forty-six radar sites feeding into four new Region Operation Control Centers (ROCCs) with FYQ-93 computer systems. With the activation of the four U.S. ROCCs and the two Canadian ROCCs, the last seven of the SAGE direction centers were deactivated and this signaled the end of the SAGE system. Of the remaining forty-six radar sites, thirty-one had FAA-operated search radars and USAF operated height finders. Five sites just had FAA search radars and only ten sites were operated by the Military. With the deployment of forty FAA ARSR-4 3D radar sets in the 1990s, the earlier military and FAA radars were replaced.

The Canadians closed their underground SAGE Direction Center and created two ROCCs (CAN-East and CAN-West) using the FYQ-93 computers in the underground facility.

Duluth SAGE Direction Center DC-10
Unit Designation Command From To
Duluth Air Defense Sector ADC 1957-10-01 1966-04-01
29th Air Division ADC 1966-04-01 1969-11-19
23rd Air Division ADC 1969-11-19 1979-10-01
23rd Air Division TAC 1979-10-01 1982-04-15
TAC 1982-04-15 1983-04-01

The Duluth SAGE Direction Center was one of the six direction centers designated as a SAGE Regional Control Centers (RCC) in 1966 and it remained operational, still using the vacuum tube FSQ-7 computers, until deactivated on 1 Apr 1983.

Duluth SAGE Direction Center DC-10 Radar Sites (edit list)
Location Type State Unit ADC NORAD JSS From To GPS Notes
Finland AFS MN 756th P-69 Z-069 1959-07-01 1980-08-15 47.45361,
Grand Rapids AFS MN 707th SM-138 Z-138 1959-07-01 1963-08-01 47.24028,
Baudette AFS MN 692nd SM-132 Z-132 1959-07-01 1979-07-01 48.66992,
Osceola AFS WI 674th P-35 Z-035 1959-07-01 1975-03-31 45.25139,
Armstrong AS ON 914th C-15 C-15 1959-11-01 1962-11-01 50.30528,
Sioux Lookout AS ON 915th C-16 C-16 1959-11-15 1962-10-01 50.08306,
Lowther AS ON 639th M-119 C-119 1963-07-01 1981-09-01 49.55583,
To RCAF 1963
Beausejour AS MB 916th
C-17 C-17 R-25 1963-09-01 1969-11-14 50.14806,
To RCAF 1961
Calumet AFS MI 665th P-16 Z-016 J-59 1963-10-01 1983-04-01 47.37111,
Antigo AFS MN 676th P-19 Z-019 1963-10-01 1964-06-01 45.04833,
Wadena AFS MN 739th P-17 Z-017 1963-09-04 1970-09-30 46.51528,
Sault Ste Marie AFS MI 753rd P-66 Z-066 1963-10-01 1979-10-30 46.45722,
Finley AFS ND 785th P-29 Z-029
J-75 1963-09-04 1969-09-15 47.51583,
Selfridge AFB MI 661st P-20 Z-020 1969-11-14 1974-07-01 42.62694,
Empire AFS MI 752nd P-34 Z-034 J-58 1969-11-14 1978-04-01 44.8025,
Chandler AFS MN 787th P-18 Z-18 1968-07-01 1969-07-01 43.89778,
Waverly AFS IA 788th P-81 Z-81 1968-07-01 1969-09-30 42.69,

Current Status

Sage Direction Center blockhouse repurposed as the Natural Resources Research Institute, University of Minnesota - Duluth, Duluth IAP in Duluth, Saint Louis County, Minnesota.

Location: Duluth IAP, Duluth, Saint Louis County, Minnesota.

Maps & Images

Lat: 46.83609 Long: -92.20731

  • Multi Maps from ACME
  • Maps from Bing
  • Maps from Google
  • Elevation: 1,428'

See Also:


  • 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 47, 127.
  • 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.
  • Ulmann, Bernd, AN/FSQ-7:the computer that shaped the Cold War, 2014, Walter de Gruyter GmbH & Co KG, ISBN 978-3-486-72766-1, 272 pages.


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