Sussex County is the northernmost county in the State of New Jersey. Its county seat is Newton. It is part of the New York City Metropolitan Area. As of the 2010 United States Census, the county had 149,265 residents, an increase of 5,099 (3.5%) from the 144,166 persons enumerated in the 2000 Census, retaining its position as the 17th-most populous county among the state's 21 counties. Based on 2010 Census data, Vernon Township was the county's largest in both population and area, with a population of 23,943 and covering an area of 70.59 square miles (182.8 km²).