| Primary address | 21 Williams Avenue, Syosset |
| Zip code | 11791 |
| County | Nassau |
| Town/City | Oyster Bay |
| Village (swiss code) | None (unincorporated town) |
| Parcel ID | 15-123-47 |
View detailed information on past sales, title documents and property taxes, including the assessed market value, in their dedicated tabs.
| Building sqft | 2,422 |
| Building class | One Family Year - Round Residence (210.01) |
| Land | Primary site |
| Topography | Level |
| Acreage | 0.169 |
| Buildings on lot | 1 |
| Year built | 1955 |
| Stories | 2 |
| Style | Colonial |
| Rooms | 9 |
| Bathrooms | 3 |
| Attic | None |
| Basement | Full |
| Exterior wall | Frame |
| Heating type | Central/AC |
| Heating system | Central w ac |
| Zoning district | Register (See more on map) |
| School district | Locust Grove |
View more neighborhood information such as transportation, nearby schools and risk designations in the dedicated tab.
Property reports include comprehensive occupancy, improvement and development information (where available).
Create a free account to access valuable data points such as:
21 Williams Avenue, Syosset, NY 11791 was built in 1955 and has a total of 2,422 square feet.
What is the assessed value of 21 Williams Avenue, Syosset, NY 11791 and the property tax paid?Assessed at $673, the tax amount paid for 21 Williams Avenue, Syosset, NY 11791 is $21,885.
When was 21 Williams Avenue, Syosset, NY 11791 last sold and what was the last sale price?21 Williams Avenue, Syosset, NY 11791 was last sold in 12/19/2024 for $990,000.
View detailed property contacts like owners, building management, representatives from permits and tenants with a free account.
Create a free account to view the complete sales history for 21 Williams Avenue, Syosset, including title documents, transfer conditions, mortgages and liens.
*Here are the three most recent sales for this property.
To view the complete history of deeds, mortgages, assignments of leases and rents, and more, sign up for free. Available data goes back to 1966.
R: Recorded date
D: Document date
Access detailed property tax data for 21 Williams Avenue, Syosset, NY 11791. Tax information included: property tax, market value and assessed value, exemptions, abatements, and assessment history.
| Tax year | 2026 |
| Property tax | $21,885 |
| Tax class | Register |
| Market value | $673,000 |
| Assessed value | $673 |
Here's the assessment & property tax history for 21 Williams Avenue, Syosset, including the evolution of the total tax rate and corresponding property tax.
| Year | Market value | Assessment value | Total tax rate | Property tax | Year over year change |
|---|---|---|---|---|---|
| 2025 | $713,000 | $713 | 3139.97 | $22,388 | -18.18% |
| 2024 | $813,679 | $814 | 3361.673 | $27,364 | -1.86% |
| 2023 | $798,000 | $798 | 3493.926 | $27,882 | -9.78% |
| 2022 | $809,000 | $809 | 3820.056 | $30,904 | -9.18% |
| 2021 | $792,000 | $792 | 4296.58 | $34,029 | +89.78% |
The complete history of permits filed for 21 Williams Avenue, Syosset, including new construction or demolition permits, plus any work pertaining to plumbing, heating and sprinkler systems is available with a free account. Available data goes back to 1990.
Create a free account to unlock extended information for 21 Williams Avenue, Syosset, including whether it's located in FEMA flood zones, floodways or special flood hazard areas, as well as the Coastal barriers resources system area (COBRA).
| FEMA flood zone(s) | X (See more on map) |
Access the detailed traffic volume map for 21 Williams Avenue, Syosset to see estimated average daily traffic on streets surrounding the property as well as the types of properties in its vicinity.
| View daily traffic map |
| Name | Rating | Type | Grade range | No of students | Distance to school (mi) |
|---|---|---|---|---|---|
| Willits Elementary School | 9 | Public | K-5 | 305 | 0.33 |
| South Grove Elementary School | 9 | Public | K-5 | 416 | 0.38 |
| Baylis Elementary School | 9 | Public | K-5 | 405 | 0.84 |
| St Edward Confessor School | NR | Private | PK-8 | 265 | 1.07 |
| St Edward Confessor School | NR | Private | PK-8 | 265 | 1.07 |
| Name | Rating | Type | Grade range | No of students | Distance to school (mi) |
|---|---|---|---|---|---|
| H B Thompson Middle School | 9 | Public | 6-8 | 997 | 0.47 |
| Fusion Academy Woodbury Ny | NR | Private | 6-12 | 75 | 1.06 |
| St Edward Confessor School | NR | Private | PK-8 | 265 | 1.07 |
| P.S. 256 | NR | Public | PK, K-12 | 500 | 1.46 |
| Plainview Old Bethpage Middle School | 8 | Public | 5-8 | 889 | 1.90 |
| Name | Rating | Type | Grade range | No of students | Distance to school (mi) |
|---|---|---|---|---|---|
| Fusion Academy Woodbury Ny | NR | Private | 6-12 | 75 | 1.06 |
| P.S. 256 | NR | Public | PK, K-12 | 500 | 1.46 |
| Our Lady Of Mercy Academy | NR | Private | 9-12 | 359 | 1.63 |
| Syosset Senior High School | 10 | Public | 9-12 | 2,266 | 2.03 |
| Good Shepherd Lutheran School | NR | Private | 0 | 2.06 |
Data provided by GreatSchools.org © 2025. All rights reserved.
Here are the neighbors for 21 Williams Avenue, Syosset.
| Address | Square feet | Purchase date | Purchase price |
|---|---|---|---|
| 5 Baird CT, Syosset | 2,180 | 01/06/2004 | $543,000 |
| 7 Baird CT, Syosset | 2,766 | 09/22/2020 | $1,204,800 |
| 15 Williams Ave, Syosset | 1,071 | 08/04/1998 | $225,000 |
| 17 Hicks Ave, Syosset | 1,071 | 05/30/2012 | $390,000 |
| 17 Williams Ave, Syosset | 2,894 | 04/03/2022 | |
| 11 Williams Ave, Syosset | 1,071 | 08/15/2000 | $117,000 |
| 2 Baird CT, Syosset | 2,872 | 12/28/2005 | $586,000 |
| 1 Baird CT, Syosset | 2,124 | ||
| 52 Underhill Ave, Syosset | 1,395 | 05/27/2022 | |
| 56 Underhill Ave, Syosset | 1,619 | 10/13/2004 | $505,000 |
| 15 Hicks Ave, Syosset | 1,071 | 01/02/1998 | |
| 42 Underhill Ave, Syosset | 1,289 | ||
| 9 Baird CT, Syosset | 2,823 | 07/19/1999 | $315,000 |
| 48 Underhill Ave, Syosset | 1,071 | 06/06/2017 | |
| 19 Hicks Ave, Syosset | 2,124 | 10/16/2025 | $950,000 |
| 9 Hicks Ave, Syosset | 2,422 | 12/03/2021 | $1,255,000 |
| 3 Baird CT, Syosset | 2,124 | 05/10/2012 | $723,000 |
| 19 Williams Ave, Syosset | 1,071 | 10/05/2023 | $825,000 |
| 11 Hicks Ave, Syosset | 2,778 | 06/26/2017 | $933,720 |
| 4 Baird CT, Syosset | 1,445 | 11/12/2025 |