Fort Baldwin is a historic military fortification in Phippsburg. It was built between 1905 and 1912 as part of the coastal defense system of the United States. The fort consists of three concrete batteries, named Hardman, Hawley, and Nye, that were designed to mount artillery guns to protect the mouth of the Kennebec River. The fort also had a fire control tower, a mine casemate, and barracks for the soldiers. Fort Baldwin was named after Jeduthan Baldwin, an engineer who served in the American Revolutionary War. The fort was active during World War I and World War II, but never fired its guns in combat. It was decommissioned in 1946 and is now a state historic site open to the public.