Winnsboro is a town in Fairfield County, South Carolina, United States. The population was 3,599 at the 2000 census. It is the county seat of Fairfield County. Winnsboro is part of the Columbia, South Carolina Metropolitan Statistical Area. Several years before the Revolution, Richard Winn from Virginia moved to what is now called Fairfield County. His lands covered the present site of Winnsboro, and as early as 1777 the settlement was known as "Winnsborough".