At the outbreak of World War II in Europe, the US Army authorized four new gun batteries for Portland Harbor, with two on Peaks Island and one each on Jewell Island and at Two Lights. Battery 201, the first battery of the 200 series, was built here in 1943 but was never given a name and never fully equipped with guns before Allied success in World War II made it unnecessary. Between its two guns stood a concrete casemate containing a planning room, ammunition storage, temporary quarters, three diesel-powered electrical generators, and a plotting room that could be sealed in the event of a poison gas attack, while the exterior was reinforced with a concrete apron, covered with earth, and carefully camouflaged. Target coordinates were telephoned to the plotting room from two nearby fire control towers, a seacoast radar installation on four concrete bases near the fog station, and a Navy Magnetic Loop Station that detected ships entering Portland Harbor. The Two Lights site also included three searchlights and two anti-aircraft guns. The six-inch guns used in 200-series batteries were mounted inside protective cast-steel shields on barbettes carriages, used modified M1003 and M1905 gun tubes about 25 feet long, and could fire projectiles as far as about 27,000 yards, or 15 miles, allowing Battery 201 to reach roughly from Yarmouth to Cape Porpoise, while other Portland harbor defense guns could reach up to 25 miles. Men in the observation tower behind the battery and in a nearby lighthouse took readings on enemy ships and radioed them to the casemate, where firing coordinates were determined. In 1961, the State of Maine purchased this scenic area from the Federal government for $67,000.