Mercer County (N.J.)

Mercer County is a county located in the U.S. state of New Jersey. Its county seat is Trenton, also the state capital, prompting its nickname The Capital County. Mercer County alone constitutes the Trenton–Princeton metropolitan statistical area and is considered part of the New York combined statistical area by the U.S. Census Bureau, but also directly borders the Philadelphia metropolitan area and is included within the Federal Communications Commission's Philadelphia Designated Media Market Area. The county is part of the Central Jersey region of the state. As of the 2020 United States census, the county retained its position as the state's 12th-most-populous county, with a population of 387,340, its highest decennial count ever and an increase of 20,827 (+5.7%) from the 366,513 recorded at the 2010 census, which in turn had reflected an increase of 15,752 (+4.5%) from the 350,761 enumerated at the 2000 census The United States Census Bureau's Population Estimates Program estimated a 2025 population of 399,289, an increase of 11,949 (+3.1%) from the 2020 decennial census. The most populous municipality in Mercer County at the 2020 census was Hamilton Township, with 92,297 residents, while Hopewell Township was the largest in area. The county was formed by an act of the New Jersey Legislature on February 22, 1838, from portions of Burlington County (Nottingham Township, now Hamilton Township), Hunterdon County (Ewing Township, Lawrence Township, Trenton, and portions of Hopewell Township), and Middlesex County (West Windsor and portions of East Windsor). The former Keith Line bisects the county and is the boundary between municipalities that previously had been separated into West Jersey and East Jersey. Trenton–Mercer Airport in Ewing Township is a commercial and corporate aviation airport serving Mercer County and its surrounding vicinity. Princeton is home to Princeton University, an Ivy League research university, and to Drumthwacket, the official residence of the governor of New Jersey. Mercer County contains 12 municipalities, the fewest of any county in New Jersey, and equal to Hudson County.