Washington County Courthouse in Blair, Nebraska; seen from the west. The Renaissance Revival building was constructed in 1889. It is listed in the National Register of Historic Places. – Ammodramus, Public domain – Wikimedia Commons Washington County is located in Nebraska. About 20,248 people live here. Between 2010 and 2020, the population grew from 20,234 to 20,865. The region is divided into 2 Municipalities and 5 Subregions. The region was founded in 1854. The name originates from George Washington (Founding Father and first U.S. president) Washington County is county in Nebraska, United States. More information at www.co.washington.ne.us.