 The United States Office of Management and Budget has designated Union County as the Lewisburg, PA Micropolitan Statistical Area (µSA).As of the 2010 census the micropolitan area ranked 12th most populous in the State of Pennsylvania and the 263rd most populous in the United States with a population of 44,947.Union County is also a part of the Bloomsburg–Berwick–Sunbury, PA Combined Statistical Area (CSA), which combines the populations of Union County, as well as Columbia, Montour, Northumberland and Snyder Counties in Pennsylvania.