Founded in 1805, Jefferson County is one of 62 counties in the state of New York. Historically, Jefferson County was formed from Oneida County. The city of Watertown is the county seat. With FIPS code of 45, Jefferson County has a population of 116,295 and area of 1,857 square miles (4,810 km2).
List of all cities in Jefferson County, NY alphabetically
| City/Town | Postal Code | Area Code |
| Adams, NY | 13605 | 315 |
| Adams Center, NY | 13606 | 315 |
| Adams Cove, NY | 13634 | 315 |
| Alex Bay, NY | 13607 | 315 |
| Alexandra Bay, NY | 13607 | 315 |
| Alexandria, NY | 13607 | 315 |
| Antwerp, NY | 13608 | 315 |
| Antwerp, NY | 13671 | 315 |
| Belleville, NY | 13611 | 315 |
| Black River, NY | 13612 | 315 |
| Boultons Beach, NY | 13685 | 315 |
| Brownville, NY | 13615 | 315 |
| Calcium, NY | 13616 | 315 |
| Cape Vincent, NY | 13618 | 315 |
| Carthage, NY | 13619 | 315 |
| Champion, NY | 13619 | 315 |
| Champion Huddle, NY | 13619 | 315 |
| Chaumont, NY | 13622 | 315 |
| Clayton, NY | 13624 | 315 |
| Collins Landing, NY | 13607 | 315 |
| Deferiet, NY | 13628 | 315 |
| Depauville, NY | 13632 | 315 |
| Dexter, NY | 13634 | 315 |
| Dexter, NY | 13657 | 315 |
| Diamond, NY | 13659 | 315 |
| East Rodman, NY | 13682 | 315 |
| Edgewood Park, NY | 13607 | 315 |
| Ellisburg, NY | 13636 | 315 |
| Evans Mills, NY | 13637 | 315 |
| Felts Mills, NY | 13638 | 315 |
| Fineview, NY | 13640 | 315 |
| Fishers Landing, NY | 13641 | 315 |
| Fort Drum, NY | 13602 | 315 |
| 13603 | 315 | |
| Frontenac, NY | 13624 | 315 |
| Glen Park, NY | 13601 | 315 |
| Great Bend, NY | 13643 | 315 |
| Grenell, NY | 13624 | 315 |
| Grindstone, NY | 13624 | 315 |
| Gt Bend, NY | 13643 | 315 |
| Guffin Bay, NY | 13634 | 315 |
| Henderson, NY | 13650 | 315 |
| Henderson Harbor, NY | 13651 | 315 |
| Herrings, NY | 13619 | 315 |
| Hounsfield, NY | 13685 | 315 |
| Jefferson Park, NY | 13650 | 315 |
| La Fargeville, NY | 13656 | 315 |
| Lafargeville, NY | 13656 | 315 |
| Le Ray, NY | 13637 | 315 |
| Limerick, NY | 13657 | 315 |
| Lorraine, NY | 13659 | 315 |
| Mannsville, NY | 13661 | 315 |
| Murray Isle, NY | 13624 | 315 |
| Muskalounge, NY | 13634 | 315 |
| Natural Brg, NY | 13665 | 315 |
| Natural Bridge, NY | 13665 | 315 |
| Omar, NY | 13656 | 315 |
| Oswegatchie, NY | 13691 | 315 |
| Oxbow, NY | 13608 | 315 |
| 13671 | 315 | |
| Paddy Hill, NY | 13615 | 315 |
| Pamelia, NY | 13637 | 315 |
| Pamelia Four Corners, NY | 13637 | 315 |
| Perch River, NY | 13634 | 315 |
| Philadelphia, NY | 13673 | 315 |
| Pierrepont Manor, NY | 13674 | 315 |
| Pillar Point, NY | 13634 | 315 |
| Plessis, NY | 13675 | 315 |
| Point Vivian, NY | 13607 | 315 |
| Redwood, NY | 13679 | 315 |
| Rodman, NY | 13682 | 315 |
| Rural Hill, NY | 13650 | 315 |
| Rutland, NY | 13638 | 315 |
| Sackets Harbor, NY | 13685 | 315 |
| Saint Lawrence Park, NY | 13607 | 315 |
| Sherwin Bay, NY | 13634 | 315 |
| Smithville, NY | 13605 | 315 |
| Stone Mills, NY | 13656 | 315 |
| Theresa, NY | 13691 | 315 |
| Thous Is Park, NY | 13692 | 315 |
| Thousand Island Park, NY | 13692 | 315 |
| Three Mile Bay, NY | 13693 | 315 |
| Watertown, NY | 13601 | 315 |
| 13602 | 315 | |
| 13603 | 315 | |
| Wegatchie, NY | 13608 | 315 |
| Wellesley Island, NY | 13640 | 315 |
| West Carthage, NY | 13619 | 315 |
| Westminster Park, NY | 13607 | 315 |
| Wilna, NY | 13619 | 315 |
| Woodville, NY | 13650 | 315 |
| Worth, NY | 13659 | 315 |
| Wtown, NY | 13601 | 315 |
| 13602 | 315 |