The United States' massive Endicott and Taft Programs of coast defense construction were no sooner complete than they faced an increasing threat.

One problem was that the disappearing carriages most of the heavy guns were mounted on limited their elevation to 10 or 15 degrees and hence their range.

Fort Saulsbury consisted of Batteries Hall and Haslet, each with two 12-inch guns and a large ammunition and fire control bunker constructed of reinforced concrete and earth.

[6][5] The fort was in caretaker status, with a maintenance garrison of about eight men, from its completion until 1939, when eight administrative buildings were authorized.

[10][5] With the construction of new batteries with 16-inch guns in World War II, almost all previous heavy weapons were scrapped by the end of 1943.

During World War II most of these batteries were enclosed in heavy concrete casemates for protection against air attack.

Also in World War II, Fort Saulsbury served as a prisoner-of-war camp for German and Italian prisoners.