There are 10 US Post Offices in Columbia County serving a total of 69,490 residents equating to 6,949 residents per post office. It's estimated that approximately 110,914 packages are handled across the 10 county post offices annually. Columbia County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 67,295. Its county seat is Bloomsburg. The county was created on March 22, 1813, from part of Northumberland County and named for Columbia, a poetic name for the United States that alludes to Christopher Columbus. Columbia County is part of the Bloomsburg-Berwick, PA Metropolitan Statistical Area."