"The AR-15 was developed in the late 1950s as a civilian weapon by Eugene Stoner, a former Marine working for small California startup called ArmaLite (which is where the AR comes from). The gun, revolutionary for its light weight, easy care and adaptability with additional components, entered the mainstream in the mid-1960s, after Colt bought the patent and developed an automatic-fire version for troops in Vietnam, called the M16."