There are 5 US Post Offices in Columbia County serving a total of 25,419 residents equating to 5,084 residents per post office. It's estimated that approximately 40,572 packages are handled across the 5 county post offices annually. Columbia County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 24,552. The county seat is Magnolia. The county was formed on December 17, 1852, and was named for Christopher Columbus. It was an alcohol prohibition or dry county. However, the voters of Columbia County voted on November 4, 2014 to make it legal to buy, sell, and manufacture alcohol within the county. The county will no longer be dry. The Magnolia, AR Micropolitan Statistical Area includes all of Columbia County."