In 1817, Walterboro was designated as the third county seat of Colleton County, and has remained such through present-day. This designation was followed by, the construction of a county courthouse and county jail in 1821. The courthouse was designed by well-known architect, Robert Mills. The town quickly spread from the original "Hickory Valley" location, after its population experienced a significant increase; this being fueled successively by, the town becoming the county seat in 1821, the establishment of a railroad line that connected the city with Columbia and Charleston in the 1880s.