List of New Jersey counties:
- Atlantic County: formed in 1837 from part of Gloucester County. County seat: Mays Landing.
- Bergen County: one of four original counties created in East Jersey in 1683. County seat: Hackensack.
- Burlington County: formed in 1694 by West Jersey. County seat: Mount Holly.
- Camden County: formed in 1844 from part of Gloucester County. County seat: Camden.
- Cape May County: formed in 1692 by West Jersey. County seat: Cape May Court House.
- Cumberland County: formed in 1748 from part of Salem County. County seat: Bridgeton.
- Essex County: one of four original counties created in East Jersey in 1683. County seat: Newark.
- Gloucester County: formed in 1686 by West Jersey. County seat: Woodbury.
- Hudson County: formed in 1840 from part of Bergen County. County seat: Jersey City.
- Hunterdon County: formed in 1714 from part of Burlington County. County seat: Flemington.
- Mercer County: formed in 1838 from parts of Burlington County, Hunterdon County, Middlesex County, and Somerset County. County seat: Trenton.
- Middlesex County: one of four original counties created in East Jersey in 1683. County seat: New Brunswick.
- Monmouth County: one of four original counties created in East Jersey in 1683. County seat: Freehold.
- Morris County: formed in 1739 from part of Hunterdon County. County seat: Morristown.
- Ocean County: formed in 1850 from part of Monmouth County. County seat: Toms River.
- Passaic County
- Salem County: formed in 1694 by West Jersey. County seat: Salem.
- Somerset County: formed in 1688 from part of Middlesex County. County seat: Somerville.
- Sussex County: formed in 1753 from part of Morris County. County seat: Newton.
- Union County: formed in 1857 from part of Essex County. County seat: Elizabeth.
- Warren County: formed in 1824 from part of Sussex County. County seat: Belvidere.