Washington County Courthouse, Machias, Maine. – Magicpiano, CC BY-SA 3.0 – Wikimedia Commons Washington County is located in Maine. About 31,625 people live here. Between 2010 and 2020, the population declined from 32,856 to 31,095. The area covers about 8,430.0 square kilometers. The region is divided into 58 Municipalities and 20 Subregions. The region was founded in 1790. The name originates from George Washington (Founding Father and first U.S. president) Washington County is county in Maine, United States. More information at washingtoncountymaine.com.