Fort Canby had barracks for enlisted men, cottages for officers and their families, and a large residence for the commanding officer, along with a post exchange, guardhouse, hospital, school, library, fire station, and gymnasium, functioning much like a small town. The U.S. Army began constructing the fort in 1863, and the first troops arrived the following year. Over the next 80 years, improvements there kept pace with changes in coast-defense technology, and the fort remained intact as a military reservation until 1948. Battery Harvey Allen preserves the interior of a typical pre-WWI American coastal fortification, and a nearby radar station site dates from WWII. Early batteries at Fort Canby were simple earthworks fronting guns, including Rodman guns and several 10-inch Parrott guns. One surviving set of foundation stones once supported "Big Betsy," a 15-inch Rodman gun first emplaced at West Battery near the Cape Disappointment Lighthouse. Smooth-bore guns such as Big Betsy had dominated artillery for centuries until the 19th century, when rifled steel guns in concrete fortifications replaced the obsolete batteries.