[3] The long-range guns of Fort Duvall could cover an arc running roughly from Gloucester in the north down to Plymouth in the south, and extending well out to sea.

Fort Duvall's guns were initially in open mounts, but were casemated in 1942 to protect against air attack.

A third pair of 16-inch guns was planned for Fort Dawes on Deer Island, but after the emplacements were constructed at the outset of WW2, the tubes for this battery were never delivered.

From 1956 to 1974 the fort was used as a Nike missile control center (B-36 C), with the launch site (B-36 L) at Webb Memorial State Park in Weymouth.

[5] In 1974 the island was turned over to the Commonwealth of Massachusetts, and was used to store school textbooks until sold to private interests for development as a gated community.