Founded in 1824, Warren County is one of 21 counties in the state of New Jersey. Historically, Warren County was formed from Sussex County. The city of Belvidere is the county seat. With FIPS code of 41, Warren County has a population of 110,731 and area of 358 square miles (927 km2).
List of all cities in Warren County, NJ alphabetically
| City/Town | Postal Code | Area Code |
| Allamuchy, NJ | 07820 | 908 |
| Allamuchy Township, NJ | 07840 | 908 |
| Alpha, NJ | 08865 | 908 |
| Belvidere, NJ | 07823 | 908 |
| Blairstown, NJ | 07825 | 908 |
| Broadway, NJ | 08808 | 908 |
| Buttzville, NJ | 07829 | 908 |
| Changewater, NJ | 07831 | 908 |
| Columbia, NJ | 07832 | 908 |
| Delaware, NJ | 07833 | 908 |
| Delaware Park, NJ | 08865 | 908 |
| Great Meadows, NJ | 07838 | 908 |
| Hackettstown, NJ | 07840 | 908 |
| Hardwick, NJ | 07825 | 908 |
| Harmony Township, NJ | 08865 | 908 |
| Hope, NJ | 07844 | 908 |
| Johnsonburg, NJ | 07846 | 908 |
| Lopatcong, NJ | 08865 | 908 |
| Oxford, NJ | 07863 | 908 |
| Phillipsburg, NJ | 08865 | 908 |
| Port Murray, NJ | 07865 | 908 |
| Stewartsville, NJ | 08886 | 908 |
| Vienna, NJ | 07880 | 908 |
| Washington, NJ | 07882 | 908 |