Question: Vails Gate, New York is part of the statistical area that contains the seat of what New Jersey county?

Context paragraphs:
Vails Gate, New York: Vails Gate is a hamlet (and census-designated place) in Orange County, New York, United States.  The population was 3,369 at the 2010 census.  It is part of the Poughkeepsie–Newburgh–Middletown, NY Metropolitan Statistical Area as well as the larger New York–Newark–Bridgeport, NY-NJ-CT-PA Combined Statistical Area.

New York State Route 300: New York State Route 300 (NY 300) is a state highway located west of the city of Newburgh in the Hudson Valley of New York in the United States.  The southern terminus of the route is at a five-way intersection with NY 32 and NY 94 in the hamlet of Vails Gate.  From there, it runs generally northwesterly through the towns of New Windsor, Newburgh, and Shawangunk, to a junction with NY 208 near the hamlet of Wallkill.  NY 300's two major changes of direction are marked by slightly unorthodox intersections with other state highways.

Newark, New Jersey: Newark ( or also locally ) is the most populous city in the U.S. state of New Jersey and the seat of Essex County.  As one of the nation's major air, shipping, and rail hubs, the city had a population of 277,140 in 2010, making it the nation's 67th most-populous municipality, after being ranked 63rd in the nation in 2000.  For 2015, the Census Bureau's Population Estimates Program calculated a population of 281,944, an increase of 1.7% from the 2010 enumeration, ranking the city the 70th largest in the nation.  Newark is the second largest city in the New York metropolitan area, located approximately 8 mi west of lower Manhattan.

Knox's Headquarters State Historic Site: Knox's Headquarters State Historic Site, in the town of New Windsor in Orange County, New York, consists of the Georgian house of the Ellison family, built in 1754, and the grounds around it.  It is located on Old Forge Hill Road, just south of Route 94 east of Vails Gate.

New Windsor Cantonment State Historic Site: The New Windsor Cantonment State Historic Site, also known as New Windsor Cantonment, is located along NY 300, north one mile of Vails Gate, in the Town of New Windsor, Orange County, New York.  The site features a reconstruction of the Continental Army's final military encampment.

Mercer County, New Jersey: Mercer County is a county located in the U.S. state of New Jersey.  Its county seat is Trenton, the state capital.  The county constitutes the Trenton-Ewing, NJ Metropolitan Statistical Area and is considered part of the New York Metropolitan Area by the United States Census Bureau, but also directly borders the Philadelphia metropolitan area and is included within the Federal Communications Commission's Philadelphia Designated Market Area.  As of the 2016 Census estimate, the county's population was 371,023, making it the state's 12th-most populous county, an increase of 1.2% from the 2010 United States Census, when its population was enumerated at 366,513, in turn an increase of 15,752 (4.5%) from the 350,761 enumerated in the 2000 Census, retaining its position as the 12th-most populous county in the state.  Mercer County stands among the highest-income counties in the United States, with the Bureau of Economic Analysis having ranked the county as having the 78th-highest per capita income of all 3,113 counties in the United States (and the sixth-highest in New Jersey) as of 2009.

Woodruff House (Cornwall, New York): The Woodruff House is located on NY 32 in Cornwall, New York, United States, a short distance south of the hamlet of Vails Gate.  It is a small stone building dating to the early 19th century.

Beacon, New York: Beacon is a city located in Dutchess County, New York, United States.  The 2010 census placed the city total population at 15,541.  Beacon is part of the Poughkeepsie–Newburgh–Middletown, New York Metropolitan Statistical Area as well as the larger New York–Newark–Bridgeport, New York–New Jersey–Connecticut–Pennsylvania Combined Statistical Area.  It was named to commemorate the historic beacon fires that blazed forth from the summit of the Fishkill Mountains to alert the Continental Army about British troop movements.

Edmonston House: The Edmonston House is located on NY 94 in the Vails Gate section of the Town of New Windsor in Orange County, New York.  It has been listed on the National Register of Historic Places since 1979.

Interstate 287: Interstate 287 (I-287) is an auxiliary Interstate Highway in the US states of New Jersey and New York.  It is a partial beltway around New York City, serving the northern half of New Jersey and the counties of Rockland and Westchester in New York.  I-287, which is signed north–south in New Jersey and east–west in New York, follows a roughly horseshoe-shaped route from the New Jersey Turnpike (I-95) in Edison Township, New Jersey, clockwise to the New England Thruway (I-95) in Rye, New York, for 98.72 mi .  Through New Jersey, I-287 runs west from its southern terminus in Edison through suburban areas.  In Bridgewater Township, the freeway takes a more northeasterly course, paralleled by U.S. Route 202 (US 202).  The northernmost part of I-287 in New Jersey passes through mountainous surroundings.  After crossing into New York at Suffern, I-287 turns east on the New York State Thruway (I-87) and runs though Rockland County.  After crossing the Hudson River on the Tappan Zee Bridge, I-287 splits from I-87 near Tarrytown and continues east through Westchester County on the Cross-Westchester Expressway until it reaches the New England Thruway.

Supporting paragraphs: Vails Gate, New York Newark, New Jersey
Answer: Essex