The AR-15 was invented in the late 1950s by American engineer Eugene Stoner. He developed the original design while working for the Armalite Corporation, and the rifle was designated as the Armalite Rifle model 15 (AR-15). The rifle featured a favorable gas tube length, weight, and performance for civilian as well as tactical use. This is why the U.S. military later adopted it and evolved the AR-15 into the M16 rifle.