There are 12 US Post Offices in Union County serving a total of 43,861 residents equating to 3,655 residents per post office. It's estimated that approximately 70,007 packages are handled across the 12 county post offices annually. Union County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 44,947. Its county seat is Lewisburg. The county was created on March 22, 1813, from part of Northumberland County. Its name is an allusion to the federal Union. Union County comprises the Lewisburg, PA Micropolitan Statistical Area, which is also included in the Bloomsburg-Berwick-Sunbury, PA Combined Statistical Area."