There are 8 US Post Offices in Saline County serving a total of 22,832 residents equating to 2,854 residents per post office. It's estimated that approximately 36,442 packages are handled across the 8 county post offices annually. Saline County is a county located along the Missouri River in the U.S. state of Missouri. As of the 2010 census, the population was 23,370. Its county seat is Marshall. The county was established November 25, 1820, and named for the region's salt springs. Settled primarily by migrants from the Upper South during the nineteenth century, this county was in the region bordering the Missouri River known as \"Little Dixie\". In the antebellum years it had plantations supported by enslaved workers. One-third of the county population was African American at the start of the American Civil War, but their proportion of the residents has declined dramatically to little more than five percent. Saline County comprises the Marshall, MO Micropolitan Statistical Area."