Dr. Richard Jordan Gatling patented his revolutionary repeater during the Civil War in late 1862. Like later models, the first gun achieved its high rate of fire by mechanical means, employing rotating barrels operated by a hand crank which fed special steel chambers, loaded with powder, bullets and backed by percussion caps, from a hopper to the mechanism. As the handle was turned, the six barrels rotated and the chambers dropped into a carrier where they were fired, one at a time, by strikers dedicated to the individual barrels. The chambers then dropped free of the gun where they could be retrieved and reloaded.
Gatling's contrivance was by no means the only machine gun that appeared during the Civil War. Most notably, there were the single-barreled Union Repeating Gun, dubbed by Abraham Lincoln the "Coffee Mill Gun" because of its resemblance to a coffee grinder, and the Ripley Gun and Requa Battery, both of which employed multiple stationary barrels.
The Gatling was actually tested and received high marks from those Army and Navy officers who witnessed it in action. But for political and logistical reasons, the gun didn't receive the attention it merited. The only Gatlings used by the Army were a dozen purchased by Federal General Benjamin F. Butler, which Gatling himself claimed to have seen action, "in repelling rebel attacks upon the Union forces€¦near Richmond, Virginia." Hearsay has it some also may have been used by the U.S. Navy Mississippi River flotilla, though there is no direct evidence to support this conjecture one way or the other.
With the emergence of the self-contained cartridge it was possible to improve the Gatling Gun even more, and without bogging the reader down with too many details (fascinating though they may be) let it suffice to say the gun ultimately became a huge success both domestically and with foreign governments, even down to today where the system is used in such military arms as the Minigun, M61 Vulcan and GAU-8.