Somerset County is a county located in the U.S. state of New Jersey. As of the 2010 United States Census, the county's population was 323,444, increasing by 25,954 (+8.7%) from the 297,490 counted in the 2000 Census, retaining its position as the state's 13th-most populous county. It is part of the New York Metropolitan Area. Its county seat is Somerville. The most populous place was Franklin Township, with 62,300 residents at the time of the 2010 Census, while Hillsborough Township, covered , the largest total area of any municipality.
Somerset County, as of the 2000 Census, was the seventh-wealthiest county in the United States by median household income at $76,933 (third in New Jersey behind Hunterdon County at $79,888 and Morris County at $77,340), fourth in median family income at $90,655 (second in New Jersey behind Hunterdon County at $91,050) and ranked seventh by per capita income at $37,970 (highest in New Jersey). The Bureau of Economic Analysis ranked the county as having the 11th-highest per capita income of all 3,113 counties in the United States (and the highest in New Jersey) as of 2009.
Somerset County was created on May 14, 1688, from portions of Middlesex County.
Somerset County is one of America's oldest counties, and is named after the English county of Somerset. The area was first settled in 1681, in the vicinity of Bound Brook, and the county was established by charter on May 22, 1688. Most of the early residents were Dutch. General George Washington and his troops marched through the county on several occasions and slept in many of the homes located throughout the area. Somerset County also played an important part during both World War I and World War II with weapons depots and the manufacturing of the army's woolen blankets.
For much of its history, Somerset County was primarily an agricultural county. In the late 19th century, the Somerset Hills area of Somerset County became a popular country home for wealthy industrialists. The area is still the home of wealthy pharmaceutical industrialists.
In the 1960s, townships that were once exclusively agricultural were quickly transformed into suburban communities. Examples include Bridgewater Township and the Watchung Hills communities of Watchung, Green Brook and Warren Township. This growth was aided by the development of the county's very strong pharmaceutical and technology presence. Warren Township used to be considered "the greenest place in New Jersey." More recently, there has been an influx of New York City commuters who use New Jersey Transit's Raritan Valley Line and Gladstone Branch or use Interstate 78.