Johnsonville is a city in Florence County, South Carolina, United States. The population was 1,480 at the 2010 census. It is part of the Florence Metropolitan Statistical Area.The city was founded in 1913 west of the spot of the former Witherspoon's Ferry on the Pee Dee River, where General Francis Marion received his commission for the Revolutionary War. Edward "Dwight" Carraway, Jr., a resident of Johnsonville from early childhood to the early 1980s, holds the record of South Carolina's youngest person ever elected to public office. He was elected Alderman in June, 1976. Also, he was a classmate of Joseph Stevens "Steve" Dukes who has served as Mayor of Johnsonville since 2004.The city is home to the Johnsonville Heritage Festival, which began in 2011 to celebrate the area's ties to the American Revolution.