On 19 December 1855, a legislative act was passed partitioning Sumter District by forming Clarendon District, with the same boundaries as defined for Clarendon County in 1785. When effectuated in 1857, a northeastern part of Sumter District (formerly in Salem County) was also separated in the partition (the area east of a line drawn from the northernmost point of old Clarendon County continued north-northeasterly to a point on the boundary line with Darlington District (Sumter County's northeastern cornerpoint abutting Florence County since 1888).