In 1958, a nuclear bomb was dropped on Mars Bluff, SC (near Florence) by the United States.
It was an accident (dude on the plane pulled the wrong handle), and the core of uranium and plutonium was removed, but it still contained 7,600 lbs of conventional explosives. It created a crater 75 feet wide by 30 feet deep, which is preserved and can be seen today. There were some people injured by the explosion, but no one was killed.