The Springfield Armory became a National Historic Site in 1974. It became a museum after it ceased operations in 1968. Based on a decision put into place in 1794 by George Washington, the U.S. established northern and southern (Harper's Ferry, VA) arms manufacturing sites as it became obvious that the U.S. could not depend on Europe to supply arms for its own security. For 174 years, Springfield was the epicenter of military small arms development and manufacture.
Interestingly, during the Civil War, Harper's Ferry was demolished, and the Confederates were forced to secure firearms from Europe. Prior to the War, the South had nearly 300,000 military firearms, enough for a short war. Some musket firearms (100,000) were manufactured at Richmond (VA) and Fayetteville (NC), while Springfield had the most advanced technology in the world.
Springfield Armory NHS has the largest collection of Confederate shoulder arms in the world. The Main Arsenal building (pictured) was used to store finished firearms. The loading dock stairwell was designed to resemble a carbine. Heavy manufacturing operations were done a mile down Walnut Ave. at the Mill River facility (bottom photo).
During WWI, the Armory produced over 265,000 Model 1903 rifles for American troops. Mass production allowed for the manufacture of 3.5million M1 rifles during WWII. Phased out in 1966, the M14 rifle was the last to be produced in Springfield.