There are 5 US Post Offices in Darlington County serving a total of 60,280 residents equating to 12,056 residents per post office. It's estimated that approximately 96,214 packages are handled across the 5 county post offices annually. Darlington County is a county located in the U.S. state of South Carolina. As of the 2010 census, its population was at 68,681. Its county seat is Darlington. Darlington County is included in the Florence, SC Metropolitan Statistical Area. The county's population was nearly 60% rural in 2000."