County · code 36045
Jefferson CountyNew York
Jefferson County is in New York, with its seat in Watertown. The county was established in 1805.
- Founded1805
- County seatWatertown
- Named forThomas Jefferson
- Land area1,269 sq mi + 589 sq mi water
- Population116,721 2020 Census
Where it is
Jefferson on the map of New York
New York has 62 counties and county equivalents, each with its own records office. Shapes with a page are links.
History
Formed in 1805 from Oneida County
An old deed may name a county that no longer exists, or a boundary that has since moved.
Jefferson County was created from Oneida County on March 28, 1805, and named after Thomas Jefferson. The county gained and lost territory to Lewis County through several boundary adjustments between 1808 and 1813.
- 1805Jefferson County created Jefferson created from Oneida. · N.Y. Laws 1804, 28th sess., ch. 51, secs. 1-2/p. 73
- 1808
- 1810
- 1813Gained territory Jefferson gained from Lewis. · N.Y. Laws 1812, 36th sess., ch. 117/p. 189
Land and parcels
What the maps cover in Jefferson
Who publishes each layer, how good it is, and when we last checked.
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Parcels Missing
No public parcel map found for Jefferson County yet. Lot lines and owners of record are kept by the county (co.jefferson.ny.us).
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Address points Official
One point per address, 63,484 in all from NYS Office of Information Technology Services (ITS), Geospatial Services / GIS Program Office (AGOL org 'ShareGIS NY', owner NYSGIS_GPO).
edited 25 September 2026 · checked 14 October 2026 -
Buildings Reference
Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026
- Official
- from the office that keeps the record
- Good enough
- a reliable statewide or national copy
- Fallback
- a guide only; check the official record
- Missing
- nothing public found yet
People and land
Jefferson by the Census
Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.
Rules and offices
Jefferson County's official site
We have found the county's site but not its offices yet; start there.
County government
- County government
The official website of Jefferson County.
See your own lot on these maps
Open Jefferson County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.
Questions
Common questions about Jefferson County
- When was Jefferson County founded?
- Jefferson County was founded in 1805, formed from Oneida County, and named after Thomas Jefferson.
- What is the county seat of Jefferson County?
- The county seat of Jefferson County is Watertown.
- Is there an online parcel map for Jefferson County?
- Not that we have found yet. Lot lines and owners of record are kept by the county assessor's office. When a public parcel map appears, it shows here.
- Has Jefferson County's boundary or name changed?
- Jefferson County was created in 1805 from Oneida County. Since then the Atlas of Historical County Boundaries records 3 later changes, chiefly involving Lewis County.
- Is my lot in a flood zone?
- We do not have flood maps for Jefferson County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.
Nearby