Barnwell County was originally part of Orangeburg District, and in 1785 it was named Winton County. It was given its current name in 1800 when it was named for John Barnwell (1748-1800), a Revolutionary War Leader. Barnwell County has decreased in size over the years as new counties were created within its boundaries (Aiken in 1871, Bamberg in 1897 and Allendale in 1919). The South Carolina Railroad, which connected Charleston to Hamburg on the Savannah River, was built through this area, creating the towns of Blackville and Williston in the mid-nineteenth century.
Early settlers to Orangeburg District: Robert McCampbell, Gabriel Moffitt, W. H. Lacy, Nathaniel Perry, and others.