Fort Wetherill was reactivated by the U.S. Army in September 1940 as a major part of the Harbor Defenses of Narragansett Bay, and new barracks were built to house the National Guard's 243rd Coast Artillery Regiment and its 1,200 soldiers.
The State of Rhode Island officially acquired the fort on 16 August 1972 and reconfigured the site for public use as a state park.