What was the first American assault rifle?

Answer 1

That depends on how you define the term "assault rifle" since there are practical definitions and legal definitions. One definition is a shoulder fired weapon capable of semi or full auto fire, fed from a detachable magazine, and firing a cartridge of lesser power than a standard military rifle. By that definition, ONE candidate for the US First Place award may be the M-2 Carbine. The M-2 was a select fire version of the M-1 Carbine. It fires the Cal 30 Carbine cartridge, and fed from a 10, 15, or 30 round magazine. It was developed during WW II.