Bombed by the Japanese in 1942, the military bases at Dutch Harbor, near Unalaska, served both the army and the navy and were the largest of the early bases in the Aleutians, pivotal to the defense of the Aleutian Chain. The United States military involvement in the Aleutians began in 1911 when the navy established a radio communication station. Although a naval aerology station was constructed in July 1939, serious buildup did not begin until the summer of 1940. Completed in 1944, the Naval Operating Base included seven docks and housing for 281 officers and 5,444 enlisted men. Albert Kahn and Associates of Detroit developed the original plan for the base, proposing a composite building with housing and work functions in connected structures. Although Kahn's plans stipulated reinforced concrete, suitable aggregate could not be found at Dutch Harbor. New plans proposed steel, but because of war shortages, wood-framed structures were finally decided upon.
The army facilities included housing for 9,976 officers and enlisted men. Here the Kahn composite buildings were shelved in favor of the standard army quartermaster plans, 700 series. These two-story, wood-framed buildings, each housing 63 men, were altered during construction to include drying rooms and arctic entries, interior wallboards, and blackout windows. Originally constructed on Amaknak Island next to the Naval Operating Base, Fort Mears expanded to Unalaska Island across the bay; eventually the army consolidated its facilities there and left Amaknak to the navy.
The hills around Dutch Harbor contain many concrete structures, half buried into the earth. Built between 1941 and 1944, these include battery command posts, two-level observation posts with rounded, concrete roofs, and the smaller pillboxes.
On 3 and 4 June 1942, the Japanese bombed Dutch Harbor, as a diversionary tactic to conceal their occupation of the islands of Attu and Kiska and as a defensive measure, to prevent attacks by the Americans against the Japanese mainland. Although 43 Americans died, the base was not appreciably damaged.
Since the navy's departure in 1947 and the army's in 1952, the extensive installation has fallen into ruin. Recent demolitions through the army's Defense Environmental Restoration Program have left only a few military buildings, some of which are mentioned below. The site was declared a National Historic Landmark in 1985.