Fort Stevens was constructed in 1863-64 during the American Civil War as an earthwork battery on the south shore of the mouth of the Columbia River, about 15 miles (24 km) north of Seaside and 6.4 miles (10 km) northwest of Astoria, at Hammond, Oregon. It was originally known as the Fort at Point Adams and named Fort Stevens in 1865 in honor of the former territorial governor of Washington, Isaac I. Stevens who had been killed in action.

Fort Stevens was the primary military installation in what became the Three Fort Harbor Defense System at the mouth of the Columbia River. The other forts were Fort Canby, built at the same time as Fort Stevens, and Fort Columbia, built between 1896 and 1904. Both are on the Washington side of the river. The forts were to defend the mouth of the Columbia from potential British attack during the Pig War and subsequent ongoing regional tensions through 1870 in the San Juan Islands. The fort was also important during the 1896-1903 Alaska Boundary Dispute when British-American tensions again were high and the two countries were on the brink of war.

During World War II, Fort Stevens again guarded the mouth of the Columbia River. On June 21, 1942, a Japanese submarine with a crew of 97, and transporting a Yokosuka seaplane, entered U.S. coastal waters following fishing boats to avoid minefields. The submarine later surfaced and opened fire on Fort Stevens with a deck gun. American Army Air Corps planes on a training mission spotted the submarine but the submarine submerged undamaged. Fort Stevens was decommissioned in 1947 and today is preserved within Fort Stevens State Park. Read more here and here. Explore more of Fort Stevens here: