Lewisburg is a borough in Union County, Pennsylvania, United States, 30 miles south by southeast of Williamsport and 60 miles north of Harrisburg. In the past, it was the commercial center for a fertile grain and general farming region. The population was 5,792 at the 2010 census. It is the county seat of Union County. Located in central Pennsylvania's Susquehanna River Valley, on the West Branch Susquehanna River, Lewisburg is northwest of Sunbury. It is home to Bucknell University and is near the Lewisburg Federal Penitentiary. Its 19th-century downtown is on the National Register of Historic Places. Lewisburg is the principal city of the Lewisburg, PA Micropolitan Statistical Area, and is also part of the larger Bloomsburg-Berwick-Sunbury, PA Combined Statistical Area.