It was established in 1873 as The Battery at Portland Head (as in Portland, Maine) as a sub-post of Fort Preble. In 1898 it became a separate and independent fort designated Fort Williams in honor of Brevet Major General Seth Williams.
Williams was a native of Maine, graduated 23rd in a class of 56 from the U.S. Military Academy in 1842, and served as an aide-de-camp to General Robert Patterson in the Mexican-American War (1846-1848). Subsequently, he became adjutant at West Point from 1850 to 1853.
He served as an Assistant Adjutant General in the Union's Army of the Potomac during the American Civil War. For you Civil War aficionados, Williams was a groomsman at Maj. Gen. George McClellan's wedding in New York City on May 22, 1860. Seth Williams served as assistant adjutant general to McClellan in the Department of the Ohio in the summer of 1861.
Also, it was Williams who took Grant's message to respectfully suggest surrender to Robert E. Lee during the Appomattox battle, and it was Williams who delivered the terms of surrender to the rebel forces. Those terms were accepted at Appomattox Court House on April 9, 1865. All pretty good reasons to honor him by naming a fort after him, huh?
Fast-forward to April, 1945 and you have an memorial here at Fort Williams of the greatest loss of U.S. Navy personnel during World War II in New England waters.