There are 7 US Post Offices in Clark County serving a total of 24,205 residents equating to 3,458 residents per post office. It's estimated that approximately 38,634 packages are handled across the 7 county post offices annually. Clark County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 22,995. The county seat is Arkadelphia. The Arkadelphia, AR Micropolitan Statistical Area includes all of Clark County."