The fort at Portland Head, which was Portland Harbor's main defense for many years, was officially named on April 13, 1899, for Major General Seth Williams, a native of Augusta who served in the Civil War.
The fort, eventually sprawling over 90 acres, included batteries, officers' quarters, barracks, a bakery, a hospital, a bandstand, a laundry, a fire station, and the Goddard Mansion. Some of these structures still stand today.
During World War I, anti-aircraft guns were added to the fort's defenses and it was fully manned by artillery companies and National Guard troops.
During World War II, Casco Bay was the home port for all the destroyers on the Atlantic coast, including the admiral's flagship. After the war, Fort Williams provided logistical and administrative support for Army activities in Maine, until it was decommissioned in 1962 and put up for sale by the government.