There are 6 US Post Offices in Prairie County serving a total of 7,703 residents equating to 1,284 residents per post office. It's estimated that approximately 12,295 packages are handled across the 6 county post offices annually. Prairie County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 8,715. The county has two county seats, Des Arc and De Valls Bluff. Prairie County was formed on October 25, 1846, and named for the Grand Prairie of eastern Arkansas."