Gatling guns were around during the Civil War. Union Army Major General Ben "The Beast" Butler (also called "spoons" for stealing silverware when he was in New Orleans) had one open up on some Corn-feds who were trading with the Union soldiers.
A New York newspaper had one and displayed it prominently during the 1863 draft riots. The rioters steered clear of the newspaper.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!