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Single Family ResidenceResidential
$1,742,420$489 / ft²
TopHap EstimateOur estimate of what this home would sell for today, based on nearby sales, the home's size and features, and local price trends. It is a starting point, not an appraisal.· confidence 93How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Aug 30, 2026
Last sold for $1,235,000 on Oct 7, 2020

21 KNOLL LN

ROSLYN HEIGHTS, NY 11577
3
Baths
3,564 ft²
Living AreaTotal finished area of the structures, from county records. Some counties include shared space like hallways or a building gym, so it may not match a listing.
0.34 ac
Lot SizeThe size of the land the home sits on, from county records.
1951
Year BuiltThe year the home was originally built, according to county records.
1
StoriesHow many floors the home has above ground.
8
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.
2
ParkingThe number of parking spaces on the property, including the garage.

Valuation

$1.7M
$1.6M low$1.9M high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$1,235,000 · Oct 7, 2020

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$28,173 (2025)
Assessed ValueThe value the county assigns to this home to calculate property tax. It is often lower than what the home would sell for.$1,056 (2026)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$463
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$593
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$1,153
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$1,056,000

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
StyleThe architectural style of the home, such as ranch or colonial.Cape Cod
CountyNASSAU
Lot (acres)The size of the land the home sits on, from county records.0.34
ConstructionThe main material the home's frame and walls are built from.Frame (Unspecified)
HeatingThe type of heating system in the home.Central
CoolingThe type of cooling or air conditioning in the home.Central
FireplaceWhether the home has a fireplace, and what kind.Yes
GarageWhether the property has a garage, and details like whether it is attached to the home.Garage, Attached
PoolWhether the property has a pool, and what kind, such as in-ground.No
FeaturesExtra features found in county records. Records are not complete everywhere, so a missing feature does not always mean the home lacks it.Deck · 144 ft²Patio · 525 ft²Porch · 60 ft²

Transaction History(1)

Sales and refinances filed with the county for this home. Not every transfer is a normal sale, so check the type before comparing prices.

Assigned SchoolsThe public schools this address is zoned for. Boundaries change, so confirm with the district before you count on it.

M
Willets Road SchoolA-
Middle · Grades 5–7 · 0.4 mi
E
North Side SchoolA-
Elementary · Grades PK–4 · 1.1 mi
H
Wheatley SchoolA
High · Grades 8–12 · 1.3 mi

District: East Williston Union Free School District

Neighborhood · ZIP 11577These are comparison scores, not percentages. 100 equals the national average, so 150 means about 50% above average.

CrimeLocal crime compared with the rest of the country, where 100 is average. It reflects things like population density, income, and how crime gets reported.66
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.107
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.101

Index scale: 100 = US average (tick). Lower is better.

Homes occupiedThe share of homes here that someone lives in. The rest sit empty, including vacation and for-sale homes.96%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.34%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.3.2%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.1.1%
PopulationHow many people live in this area.12,075
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.3,980 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$184,838
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$245,584
Average tempThe average temperature here across a full year.53°F
Annual precipHow much rain and melted snow falls here in a typical year.49 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.56%

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Data by ATTOM. Valuations are automated estimates, not appraisals. Photos from Google Street View and may not depict the current property state.

How this home compares

21 Knoll Ln measured against every home in its neighborhood, its ZIP code and its county, using county assessor records refreshed nightly. A home can stand out in one of those areas and look ordinary in another, because each one holds a different mix of homes.

  • Worth more than 91% of homes in Nassau County
  • Costs less per square foot than 93% of homes in Roslyn Heights
  • Bigger than 94% of homes in Nassau County
  • Has a bigger lot than 92% of homes in Nassau County

What homes are worth in Roslyn Heights 11577

Each bar is how many homes fall in that price range. The marker is this home.

This home
$748K$3.1M

This home is worth more than 72% of homes in Roslyn Heights 11577.

How it measures up in Roslyn Heights 11577

The dot is this home. The mark in the middle is the typical home in Roslyn Heights 11577.

Estimated value$1,742,420
CheaperTypical $1,415,172Pricier

Pricier than 72% of homes nearby

Price per ft²$489
CheaperTypical $611Pricier

Pricier than 9% of homes nearby

Living area3,564 ft²
SmallerTypical 2,398 ft²Bigger

Bigger than 82% of homes nearby

Lot size0.34 ac
SmallerTypical 0.24 acBigger

Bigger than 82% of homes nearby

Year built1951
OlderTypical 1951Newer

Newer than 57% of homes nearby

How 21 Knoll Ln ranks against every home in each area.
MeasureThis homeRoslyn HeightsRoslyn Heights 11577Nassau County
Estimated valuepricier than$1,742,42068% of homes72% of homes91% of homes
Price per ft²pricier than$4897% of homes9% of homes40% of homes
Living areabigger than3,564 ft²76% of homes82% of homes94% of homes
Lot sizebigger than0.34 ac83% of homes82% of homes92% of homes
Year builtnewer than195151% of homes57% of homes49% of homes

About 21 Knoll Ln

How much is 21 Knoll Ln, Roslyn Heights, NY worth?

The TopHap Estimate for 21 Knoll Ln, Roslyn Heights, NY is $1,742,420 as of Aug 30, 2026. The likely range is $1,616,427 to $1,868,413. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21 Knoll Ln, Roslyn Heights, NY last sell?

21 Knoll Ln, Roslyn Heights, NY last sold on Oct 7, 2020 for $1,235,000, according to the county's recorded deed.

How big is 21 Knoll Ln, Roslyn Heights, NY?

21 Knoll Ln, Roslyn Heights, NY has 3 bathrooms, 3,564 square feet of living space and a 0.34-acre lot.

When was 21 Knoll Ln, Roslyn Heights, NY built?

21 Knoll Ln, Roslyn Heights, NY was built in 1951, making it 75 years old. It is a cape cod home. The building has 1 story.

What schools serve 21 Knoll Ln, Roslyn Heights, NY?

21 Knoll Ln, Roslyn Heights, NY is assigned to Willets Road School (middle), rated A-; North Side School (elementary), rated A-; Wheatley School (high), rated A. All sit in East Williston Union Free School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21 Knoll Ln, Roslyn Heights, NY compare to other homes in Roslyn Heights 11577?

Among the 3,676 homes in Roslyn Heights 11577, it is worth more than 72% of them ($1,742,420 against a typical $1,415,172), its price per square foot is higher than 9% of them ($489 against a typical $611), it is bigger than 82% of them (3,564 ft² against a typical 2,398 ft²), its lot is bigger than 82% of them (0.34 ac against a typical 0.24 ac) and it is newer than 57% of them (1951 against a typical 1951). Measured against all of Nassau County, it is worth more than 91% of homes there. These shares are recounted nightly from the full county assessor record for each area, not from active listings.

What are the property taxes on 21 Knoll Ln, Roslyn Heights, NY?

The 2025 property tax bill for 21 Knoll Ln, Roslyn Heights, NY was $28,173. The county assessed it at $1,056.

More homes on Knoll Ln

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Assigned schools

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