There are 25 US Post Offices in Sussex County serving a total of 150,415 residents equating to 6,017 residents per post office. It's estimated that approximately 240,079 packages are handled across the 25 county post offices annually. 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. The county had a Census-estimated population of 143,673 in 2015, a 3.7% decrease from the 149,265 enumerated in the 2010 United States Census, in turn an increase of 5,099 (3.5%) over 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). As of 2010 The Bureau of Economic Analysis ranked the county as having the 131st-highest per capita income ($49,207) of the 3,113 counties in the United States (and the ninth-highest in New Jersey). The county was established in 1753 and named after historic County Sussex, England. Because of its topography, Sussex County has remained a relatively rural and forested area. The county is part of the Skylands Region, a term promoted by the New Jersey Commerce, Economic Growth, & Tourism Commission to encourage tourism. In the western half of the county, several state and federal parks have kept the large tracts of land undeveloped and in their natural states. The eastern half of the county has had more suburban development because of its proximity to more populated areas and commercial development zones. Until the mid-20th century, most of Sussex County's economy was based on agriculture (chiefly dairy farming) and the mining industry. With the decline of these industries in the 1960s, Sussex County was transformed into a bedroom community that absorbed population shifts from New Jersey's urban areas. Recent studies estimate that 60 percent of Sussex County residents work outside of the county, many seeking or maintaining employment in New York City or New Jersey's more suburban and urban areas."