Fort Williams, covering 90 acres of land in Cape Elizabeth, was established to act as a sub-post to Fort Preble at Spring Point in South Portland. In 1899, the fort was named in honor of the late Major-General Seth Williams, who was an Assistant Adjutant-General to the United States Army.

Fort Williams is pictured fully manned by U.S. National Guard members, who were stationed there during World War I. Additionally, men from Coast Artillery Corps were stationed there to install needed weapons and machinery.

Disappearing guns were built into their defenses as anti-aircraft precautions should any European attacks be sent stateside.