I'd never heard of it, but came across an interesting article in the August 14th SC Now about efforts being made in Florence to make sure that its site remains undeveloped.
During the Civil War, there was a fear that Union gunboats would ascend the Pee Dee River and destroy the plantations producing rice. Confederate General William W. Hardee (and I didn't know that Florence, SC was named after his daughter) found a suitable area along the river to place obstructions and artillery.
The site selection wasn't too popular as it was believed that the river was so shallow here that any Union ships coming up it wouldn't be able to mount cannons. The editorial referred to it as Fort Finger, probably after J. F. Finger of Florence who was foreman of the carpenters.
Local planters who had their slaves work on the fortifications were paid $1 a day. If a horse was supplied, the planter got $5
Archaeologists haven't found any military items yet other than the remains of trenches and magazine pits. The obstructions were rafts chained together and they are long gone.
Sounds Like It Was More of a Fort If Artillery was Mounted. --Old B-Runner