Seneca County, New York
A county in New York, ranked 57 of 62 by population.
CountyFIPS 36099
- Population
- 32,883
- -562 (-1.7%) since 2020
- Land area
- 323.7
- square miles. A further 17.1% of the total area is water
- Population density
- 102
- people per square mile, computed rather than published
- County seat
- Waterloo
- Seat of county government.
- Established
- 1804
- 221 years ago
- Largest city
- Waterloo village
- Population 4,674.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.
Satellite view
Aerial imagery of Seneca County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.
Where Seneca County ranks
Position among the 62 counties of New York, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.
| Measure | Value | In New York | Nationally |
|---|---|---|---|
| Population | 32,883 | 57th of 62 | 1,380th of 3,144 |
| Land area | 323.7 sq mi | 53rd of 62 | 2,753rd of 3,144 |
| Population density | 102 per sq mi | 34th of 62 | 891st of 3,144 |
| Median household income | $68,089 | 45th of 62 | 1,335th of 3,143 |
Full data for Seneca County
| Measure | Value | Source and vintage |
|---|---|---|
| Population | 32,883 | Vintage 2025 Population Estimates |
| Population in 2020 | 33,445 | Vintage 2025 Population Estimates |
| 2020 estimates base? | 33,824 | Vintage 2025 Population Estimates |
| Land area | 323.7 sq mi | 2025 Gazetteer Files |
| Water area | 66.7 sq mi | 2025 Gazetteer Files |
| Total area | 390.4 sq mi | 2025 Gazetteer Files |
| Population density? | 102 per sq mi | Computed: Vintage 2025 estimates divided by 2025 Gazetteer land area |
| Median household income | $68,089 | American Community Survey 2020-2024 5-Year Estimates |
| Median home value | $155,400 | American Community Survey 2020-2024 5-Year Estimates |
| Median age | 43.0 | American Community Survey 2020-2024 5-Year Estimates |
| Households | 13,606 | American Community Survey 2020-2024 5-Year Estimates |
| Housing units | 16,194 | American Community Survey 2020-2024 5-Year Estimates |
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.
How the population changed
The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:
- Births minus deaths
- -27
- 342 births, 369 deaths
- Net migration
- +240
- More people moved in than moved out.
Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.
The 6 areas bordering Seneca County
Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.
| Bordering area | State | Shared border | Population |
|---|---|---|---|
| Cayuga County | New York | 30 mi | 74,365 |
| Ontario County | New York | 19 mi | 113,130 |
| Yates County | New York | 17 mi | 24,547 |
| Wayne County | New York | 13 mi | 91,250 |
| Tompkins County | New York | 12 mi | 104,047 |
| Schuyler County | New York | 10 mi | 16,924 |
Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.
All 62 counties of New York
Open the interactive New York county map, or jump straight to any of them.
- Albany County
- Allegany County
- Bronx County
- Broome County
- Cattaraugus County
- Cayuga County
- Chautauqua County
- Chemung County
- Chenango County
- Clinton County
- Columbia County
- Cortland County
- Delaware County
- Dutchess County
- Erie County
- Essex County
- Franklin County
- Fulton County
- Genesee County
- Greene County
- Hamilton County
- Herkimer County
- Jefferson County
- Kings County
- Lewis County
- Livingston County
- Madison County
- Monroe County
- Montgomery County
- Nassau County
- New York County
- Niagara County
- Oneida County
- Onondaga County
- Ontario County
- Orange County
- Orleans County
- Oswego County
- Otsego County
- Putnam County
- Queens County
- Rensselaer County
- Richmond County
- Rockland County
- Saratoga County
- Schenectady County
- Schoharie County
- Schuyler County
- Seneca County
- St. Lawrence County
- Steuben County
- Suffolk County
- Sullivan County
- Tioga County
- Tompkins County
- Ulster County
- Warren County
- Washington County
- Wayne County
- Westchester County
- Wyoming County
- Yates County
Data on this page last rebuilt 30 August 2026. How these figures are produced.