[2] It was built to protect Casco Bay, particularly Portland harbor, from Kennebunk to Popham Beach in Phippsburg.

[3] According to Kim MacIsaac and historian Joel Eastman in An Island at War, “Battery Steele is not only the largest gun battery built on Peaks Island, but also an example of the largest battery ever built anywhere in the United States.”[4] In 1995, after decades of non-use, the Peaks Island Land Preserve, a community land preservation group, formed to purchase the area and forever preserve it as a public space.

[2][5] Another two-gun 16-inch battery, Battery Construction Number (BCN) 101, was planned for the Cape Elizabeth Military Reservation near Two Lights State Park, but was cancelled as the threat to the US East Coast from surface ships was nearly non-existent by 1943.

Positions for a total of ten Anti-Motor Torpedo Boat (AMTB) batteries with 90 mm guns were constructed in Casco Bay.

All US coast defenses were abandoned and most of the guns scrapped shortly after World War II.