| County | County Seat | Created | Formed from | County Coordinator |
| Atlantic County | Mays Landing | 1837 | Gloucester County | |
| Bergen County | Hackensack | 1683 | One of four original counties created in East Jersey | |
| Burlington County | Mount Holly | 1694 | One of two original counties created in West Jersey | |
| Camden County | Camden | 1844 | Gloucester County | |
| Cape May County | Cape May Court House | 1692 | Burlington County | |
| Cumberland County | Bridgeton | 1748 | Salem County | |
| Essex County | Newark | 1683 | One of four original counties created in East Jersey | |
| Gloucester County | Woodbury | 1686 | Burlington County | |
| Hudson County | Jersey City | 1840 | Bergen County | |
| Hunterdon County | Flemington | 1714 | Burlington County | |
| Mercer County | Trenton | 1838 | Burlington County, Hunterdon County, Middlesex County, and Somerset County | |
| Middlesex County | New Brunswick | 1683 | One of four original counties created in East Jersey | |
| Monmouth County | Freehold Borough | 1683 | One of four original counties created in East Jersey | |
| Morris County | Morristown | 1739 | Hunterdon County | |
| Ocean County | Toms River | 1850 | Monmouth County | |
| Passaic County | Paterson | 1837 | Bergen County and Essex County | |
| Salem County | Salem | 1694 | One of two original counties created in West Jersey | |
| Somerset County | Somerville | 1688 | Middlesex County | |
| Sussex County | Newton | 1753 | Morris County | |
| Union County | Elizabeth | 1857 | Essex County | |
| Warren County | Belvidere | 1824 | Sussex County |