The son of an inventor, Gatling was born in Hertford County, North Carolina and by the age of 21 had invented the screw propellor for steamboats, only to discover it had recently and independently been patented by someone else.
Gatling graduated from Ohio Medical College in 1850 but was more interested in continuing his career as an inventor than in practicing medicine. He invented the Gatling gun after he noticed the majority of dead returning from the American Civil War died of illness, rather than gunshots. In 1877, he wrote: "It occurred to me that if I could invent a machine - a gun - which could by its rapidity of fire, enable one man to do as much battle duty as a hundred, that it would, to a large extent supersede the necessity of large armies, and consequently, exposure to battle and disease [would] be greatly diminished."
He founded the Gatling Gun Company in Indianapolis, Indiana in 1862, and the company merged with Colt in 1897.
Gatling died in New York City in 1903. His best-known invention would be declared obsolete by the U.S. Army eight years later, in 1911.