There are 4 US Post Offices in Dallas County serving a total of 8,201 residents equating to 2,050 residents per post office. It's estimated that approximately 13,090 packages are handled across the 4 county post offices annually. Dallas County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 8,116, making it the fourth-least populous county in Arkansas. The county seat is Fordyce. Dallas County is Arkansas's 49th county, formed on January 1, 1845, and named for George M. Dallas, Vice President of the United States."