County · code 36099
Seneca CountyNew York
Seneca County is a county in New York, with its seat in Waterloo. The county was formed on March 24, 1804.
- Founded1804
- County seatWaterloo
- Named forSeneca
- Land area324 sq mi + 67 sq mi water
- Population33,814 2020 Census
Where it is
Seneca 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 1804 from Cayuga County
An old deed may name a county that no longer exists, or a boundary that has since moved.
Seneca County was created from Cayuga County and named after the Seneca people. The county's boundaries changed several times: it lost territory to the creation of Tompkins County in 1817, then regained some in 1819, lost more to the creation of Wayne County in 1823, and gained territory from Ontario and Yates in 1828. In 1946, Seneca County lost territory to Yates County.
- 1804Seneca County created Seneca created from Cayuga. · N.Y. Laws 1804, 27th sess., ch. 31/p. 112
- 1817Lost territory Seneca lost to creation of Tompkins. · N.Y. Laws 1816, 40th sess., ch. 189, sec. 1/p. 197
- 1819Gained territory Seneca gained from Tompkins. · N.Y. Laws 1819, 42d sess., ch. 190/p. 239
- 1823Lost territory Seneca lost to creation of Wayne. · N.Y. Laws 1823, 46th sess., ch. 138, sec. 1/p. 158
- 1828Gained territory Seneca gained from Ontario and Yates. · N.Y. Rev. Stat., 3:14-15
- 1946
Land and parcels
What the maps cover in Seneca
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 Seneca County yet. Lot lines and owners of record are kept by the assessor's office.
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Address points Official
One point per address, 17,996 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
Seneca 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
Who to ask before you build, dig or sell
Official county pages only. We link to them; we do not copy them, because they change.
Inside a city or town, permits usually come from that city rather than the county.
Records
- Assessor and property records
Real Property Tax
- Clerk of court: deeds and plats
County Clerk
Permits
Zoning and code
- Planning and zoning
Planning & Community Development
County government
- County government
The official website of Seneca County.
See your own lot on these maps
Open Seneca 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 Seneca County
- When was Seneca County founded?
- Seneca County was founded in 1804, formed from Cayuga County, and named after Seneca.
- What is the county seat of Seneca County?
- The county seat of Seneca County is Waterloo.
- Is there an online parcel map for Seneca County?
- Not that we have found yet. Lot lines and owners of record are kept by the assessor's office. When a public parcel map appears, it shows here.
- Has Seneca County's boundary or name changed?
- Seneca County was created in 1804 from Cayuga County. Since then the Atlas of Historical County Boundaries records 5 later changes, chiefly involving Tompkins County, Yates County and Ontario County.
- Who issues building permits in Seneca County?
- The county's page on building permits: Seneca County Unified Solar Permit (PDF). Inside a city or town, ask that city first.
- Who issues septic and well permits in Seneca County?
- The county's page on septic systems and wells: Mental Health & Addictions.
- Is my lot in a flood zone?
- We do not have flood maps for Seneca County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.
Nearby