Battery AMTB 970

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Battery AMTB 970 (1943-1945) - Battery AMTB 970 was a reinforced concrete World War II AMTB rapid fire 90mm gun battery on Bailey Island Military Reservation, Cumberland County, Maine. Battery construction started in 1943, was completed in 1943 and transferred to the Coast Artillery for use in 1943. Deactivated in 1945.

World War II

Part of the Harbor Defense of Portland, Maine.
The AMTB battery at Bailey Island consisted of two 90mm guns mounted on 90mm M3 fixed gun mounts, two 90mm guns mounted on 90mm M1A1 mobile gun mounts and two 37mm guns mounted on M3 mobile mounts. Concrete pads were provided for both fixed guns and often wooden gun platforms were provided for the mobile guns. Two earth covered concrete magazines provided protection for the ammunition. Electric power was provided by M-7 portable generators.

The battery had a dual mission of defense against fast enemy motor torpedo boats and enemy aircraft. The effective range of the guns was about 8,000 yards or 4.5 miles. Each weapon required a crew of 15, 9 men in the gun squad and 6 men in the ammunition squad.

AMTB Front View
AMTB Interior View
AMTB Side View
AMTB Back View

The above photos were taken at Fort Monroe, Battery Parrott

From FM 4-91: "This weapon consists of the 90-mm gun M1 and top carriage M1A1 on the 90-mm gun mount M3. The mount M3 is of the turret type, the shielding being constructed of boiler plates. This boiler plate shield provide fragmentation protection only. No shielding is provided at the rear due to the requirements for service of the piece. A sighting port in the shielding in front permits sighting in direction by the gun pointer."


  • FM 4-91 - 90-MM Gun, Fixed Mount Service of the Piece
  • FM 4-126 - Antiaircraft Artillery, Service of the Piece, 90-mm Antiaircraft Gun
  • TM 9-373 - 90-mm Gun M1 and 90-mm Gun Mount T3 (M3)

Current Status

On private property. No period gun or mounts in place.

Location: Bailey Island Military Reservation, Cumberland County, Maine

Maps & Images

Lat: 43.717347 Long: -70.006031

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


  • U.S. Army Corps of Engineers, FUDS Archives Search Report, Findings, Bailey Island Fire Control Station, Harpswell, Maine, Project No. D01ME009801, October 1995. Large PDF Download
  • U.S.Army, Supplement to the Harbor Defense Project of Portland, Maine, (HDPB-AN-45), 11 Apr 1945, CDSG


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