Battery AMTB 961

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Battery AMTB 961 (1943-1946) - Battery AMTB 961 was a reinforced concrete World War II AMTB rapid fire 90mm gun battery on Fort Williams (1), Cumberland County, Maine. Battery construction started 18 Feb 1943, was completed 7 Jul 1943 and transferred to the Coast Artillery for use 27 Nov 1943 at a cost of $10,920.85. Deactivated in 1946. Assigned Location ID ME00077.

Fort Williams AMTB Battery 961 Emplacement #1 Location
Fort Williams AMTB Battery 961 Emplacement #2 from the Front
Fort Williams AMTB Battery 961 Emplacement #2 from the Rear

World War II

Part of the Harbor Defense of Portland, Maine.

The AMTB battery at Fort Williams (1) consisted of two 90mm guns mounted on 90mm M3 fixed gun mounts and two 90mm guns mounted on 90mm M1A1 mobile gun mounts. Concrete pads were provided for both fixed guns and often wooden gun platforms were provided for the mobile guns. Two earth covered magazines provided protection for the ammunition. Electric power was provided by two M-7 auxiliary generators. A small 11' by 11' BC Station was provided between the two earth-covered magazines.

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)

Battery AMTB 961 Armament (edit list)
Model Serial
Manufacturer Carriage Service
F1 90mm Rifle 186.15" M1 1453 Watervliet Pedestal Mount, M3, #24, R. Hoe 1943-1946
F2 90mm Rifle 186.15" M1 6811 Chevrolet Pedestal Mount, M3, #46, R. Hoe 1943-1946
Source: RCW Form 1, 21 Apr 1945, CDSG, Berhow, Mark A. ed, American Seacoast Defenses: A Reference Guide, 2nd Edition, CDSG Press, McLean, VA, 2004, ISBN 0-9748167-0-1, pages 80-81
Battery AMTB 961 Plan

Current Status

No period guns or mounts in place. Gun emplacement #2 is exposed but gun emplacement #1 is covered with shrubbery and cedar chips.

Location: Fort Williams Park, Cumberland County, Maine.

Maps & Images

Lat: 43.622021 Long: -70.208658


  • U.S.Army, Supplement to the Harbor Defense Project of Portland, Maine, (HDPB-AN-45), 11 Apr 1945, CDSG


Visited: 5 Jun 2013

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