There are 5 US Post Offices in Columbia County serving a total of 133,967 residents equating to 26,793 residents per post office. It's estimated that approximately 213,826 packages are handled across the 5 county post offices annually. Columbia County is a county located in the US state of Georgia. As of 2013, the population was 135,416. The legal county seat is Appling, but the location of Columbia County's government and courts is Evans. Columbia County is included in the Augusta-Richmond County, GA-SC Metropolitan Statistical Area, and is currently one of the fastest-growing counties in the United States. It is located along the Savannah River."