County outline
Where Jefferson County is located
Area breakdown
Land accounts for 68.3% of Jefferson County’s measured area and water for 31.7%. Its combined area converts to 4,808.5 square kilometers or approximately 1,188,197 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 1,267.932 | 3,283.929 | 811,476.5 |
| Water | 588.626 | 1,524.534 | 376,720.6 |
| Total | 1,856.558 | 4,808.463 | 1,188,197.1 |
How Jefferson County compares
By original Census land area, Jefferson County ranks #10 of 62 in New York and #477 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.94 times the New York county-equivalent median of 653.7 square miles. It accounts for 2.7% of the combined county land area in the state.
See the complete New York ranking · What counts as a county equivalent?
Population and density of Jefferson County
The Census Bureau estimates that 111,540 people lived in Jefferson County on July 1, 2025. That ranks #579 of 3,222 county equivalents nationally and #26 of 62 in New York. Since the April 1, 2020 estimates base of 116,710, the population has declined by 5,170 (−4.4%), compared with −1% for New York as a whole.
With 1,267.9 square miles of land, that is 88 people per square mile (34 per km²), placing Jefferson County #1,088 nationally for density and #41 in New York. The median county equivalent has 47 people per square mile; the New York median is 112. Put another way, there are about 7.3 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 116,075 | 117,019 | 115,493 | 113,280 | 112,795 | 111,540 |
| Change | — | +944 | −1,526 | −2,213 | −485 | −1,255 |
U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.
Cities and towns in Jefferson County
Jefferson County is divided into 23 cities and towns. In New York, county subdivisions are local governments, and together they cover all of the county’s land and residents.
The most populous is Le Ray town, with 24,259 residents (21.7% of the county). The largest by land is Antwerp town, at 106 mi², or 8.4% of the county’s land. The county seat, Watertown city, has 23,517 residents.
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Le Ray town | 24,259 | −5.2% | 73.6 | 5.8% |
| Watertown cityCounty seat | 23,517 | −4.7% | 9.032 | 0.7% |
| Brownville town | 5,698 | −2.6% | 58.9 | 4.6% |
| Wilna town | 5,492 | −4.1% | 78 | 6.2% |
| Watertown townCounty seat | 5,364 | −9.1% | 35.7 | 2.8% |
| Adams town | 4,826 | −3% | 42.2 | 3.3% |
| Clayton town | 4,539 | −4.7% | 82.5 | 6.5% |
| Champion town | 4,436 | −2.8% | 44 | 3.5% |
| Alexandria town | 3,632 | −2.9% | 72.6 | 5.7% |
| Ellisburg town | 3,261 | −2.7% | 85.2 | 6.7% |
| Pamelia town | 3,238 | −3.3% | 34.1 | 2.7% |
| Hounsfield town | 3,174 | −3% | 49 | 3.9% |
| Rutland town | 2,952 | −2.5% | 45.2 | 3.6% |
| Orleans town | 2,721 | −2.7% | 71.3 | 5.6% |
| Theresa town | 2,572 | −2.8% | 65.1 | 5.1% |
Show the other 8 subdivisions
| Name | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Cape Vincent town | 2,439 | −12.1% | 56.3 |
| Lyme town | 2,199 | −4.3% | 55.9 |
| Philadelphia town | 1,937 | −1.9% | 37.7 |
| Antwerp town | 1,641 | −2.6% | 106 |
| Henderson town | 1,400 | −2.8% | 41.2 |
| Rodman town | 1,151 | −2.8% | 42.3 |
| Lorraine town | 896 | −2.8% | 39 |
| Worth town | 196 | −3% | 43.3 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Jefferson County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Jefferson County is a central county of the Watertown-Fort Drum, NY Metropolitan Statistical Area. Jefferson County is the area’s only county equivalent, so the metro area has the same 1,267.9 square miles of land. By combined land it ranks #247 of 393 metropolitan areas, and #350 by population.
ZIP codes
43 ZIP Code Tabulation Areas have land in Jefferson County; 38 of them have most of their land inside the county, and the others mainly cover neighboring areas.
13083136011360213603136051360613607136081361113612136151361613618136191362213624136261362813632136341363613637136381364013641136421364313646136501365113656136591366113665136731367413675136791368213685136911369213693
ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.
Counties bordering Jefferson County
Jefferson County shares a land border with 3 county equivalents. It has more land than 1 of them. The largest neighbor is St. Lawrence County (2,679.5 mi²) and the smallest is Oswego County (951.6 mi²). Together with its neighbors, Jefferson County forms a block of 6,175.4 mi² of land, of which it holds 20.5%.
| Bordering county equivalent | Land mi² | Size vs. Jefferson | Compare |
|---|---|---|---|
| St. Lawrence County | 2,679.5 | 2.1× larger | Compare |
| Lewis County | 1,276.3 | about the same | Compare |
| Oswego County | 951.6 | 1.3× smaller | Compare |
How big is Jefferson County compared with U.S. states?
Jefferson County has more land than 1 of the 50 states. It is about 1.2 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.5 times as much land (1,948.6 mi²). New York’s county land could hold about 37 areas the size of Jefferson County.
Another way to picture it: the same land area would fill a square about 35.6 miles (57.3 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.
State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.
What stands out about Jefferson County?
Jefferson County has more land than 2,745 of the other 3,221 county equivalents in the dataset.
A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.
Does including water change its rank?
Using land plus water places Jefferson County at #355 nationally by total area, 122 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.
Its water share is 31.7%, compared with a national county-equivalent median of 1.2% — 30.5 percentage points higher. This describes the statistical geography’s land/water mix, not flood exposure or developable land.
Closest positions in the national land ranking
These entries sit immediately beside Jefferson County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #476 | Boundary County, Idaho | 1,268.7 | Compare |
| #477 | Jefferson County, New York | 1,267.9 | This county |
| #478 | Coleman County, Texas | 1,263 | Compare |
Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.
Representative coordinates
The Census internal point is 43.996389, -76.052968. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 3,283,928,401 m²; AWATER: 1,524,534,721 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Jefferson County?
Jefferson County, New York has 1,267.9 square miles (3,283.9 km²) of land and 588.6 square miles of water, for a total area of 1,856.6 square miles. It ranks #477 of 3,222 U.S. county equivalents by land area.
Is Jefferson County the largest county in New York?
No. Jefferson County ranks #10 of 62 in New York by land area. The largest is St. Lawrence County, with 2,679.5 square miles of land.
What counties border Jefferson County?
Jefferson County shares a land border with Lewis County, St. Lawrence County, and Oswego County.
What is the population of Jefferson County?
The Census Bureau estimates Jefferson County had 111,540 residents on July 1, 2025, ranking #579 of 3,222 county equivalents. That is 88 people per square mile of land.
What is the county seat of Jefferson County?
The county seat of Jefferson County is Watertown.
What cities and towns are in Jefferson County?
Jefferson County has 23 county subdivisions (cities, towns and townships). The most populous five are Le Ray town, Watertown city, Brownville town, Wilna town, and Watertown town.
Is Jefferson County part of a metropolitan area?
Yes. It is a central county of the Watertown-Fort Drum, NY Metropolitan Statistical Area.
How many ZIP codes are in Jefferson County?
43 ZIP Code Tabulation Areas have land in Jefferson County, and 38 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Jefferson County compare with U.S. states?
It has more land than 1 of the 50 states, including Rhode Island (1,033.9 square miles of land).
How many acres of land are in Jefferson County?
The land measurement converts to approximately 811,476 acres. Including water, total area is approximately 1,188,197 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.