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Single Family ResidenceResidential
$813,542
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 94How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Sep 24, 2026
Last sold for $549,000 on Aug 27, 2018

21 HARBOR AVE

ISLIP, NY 11751
0
Baths
0.17 ac
Lot SizeThe size of the land the home sits on, from county records.

Valuation

$814K
$766K low$861K high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$549,000 · Aug 27, 2018

Tax & Assessment

Assessed ValueThe value the county assigns to this home to calculate property tax. It is often lower than what the home would sell for.$47,400 (2024)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$8,700
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$38,700
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$47,400
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$667,605

Climate Risk

Projected Flood DepthHow deep a serious flood is expected to get here at some point in the next 30 years. Shown in inches.77 in
30-Year Flood ChanceThe chance of at least one serious flood here in the next 30 years, not in any single year.75%
FEMA Flood ZoneFEMA's flood zone for this address. Zones starting with A or V are high risk, and lenders usually require flood insurance there.minimal

Scores 0–100; higher = greater projected risk.

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
CountySuffolk
Lot (acres)The size of the land the home sits on, from county records.0.17
HeatingThe type of heating system in the home.None
PoolWhether the property has a pool, and what kind, such as in-ground.No

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
Islip Middle SchoolC+
Middle · Grades 7–8 · 0.3 mi
H
Islip High SchoolB+
High · Grades 9–12 · 0.5 mi
E
Wing Elementary School
Elementary · Grades KG–1 · 1.3 mi

District: Islip Union Free School District

Neighborhood · ZIP 11751These 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.59
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.102
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.69

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.97%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.19%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.4.2%
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.15,527
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.3,057 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$119,597
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$137,797
Average tempThe average temperature here across a full year.52°F
Annual precipHow much rain and melted snow falls here in a typical year.48 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.58%

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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 Harbor Ave 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 85% of homes in Islip
  • Has a smaller lot than 87% of homes in Islip

What homes are worth in Islip 11751

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

This home
$465K$1.8M

This home is worth more than 81% of homes in Islip 11751.

How it measures up in Islip 11751

The dot is this home. The mark in the middle is the typical home in Islip 11751.

Estimated value$813,542
CheaperTypical $641,189Pricier

Pricier than 81% of homes nearby

Lot size0.17 ac
SmallerTypical 0.24 acBigger

Bigger than 16% of homes nearby

How 21 Harbor Ave ranks against every home in each area.
MeasureThis homeIslipIslip 11751Suffolk County
Estimated valuepricier than$813,54285% of homes81% of homes67% of homes
Lot sizebigger than0.17 ac13% of homes16% of homes17% of homes

About 21 Harbor Ave

How much is 21 Harbor Ave, Islip, NY worth?

The TopHap Estimate for 21 Harbor Ave, Islip, NY is $813,542 as of Sep 24, 2026. The likely range is $766,259 to $860,825. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21 Harbor Ave, Islip, NY last sell?

21 Harbor Ave, Islip, NY last sold on Aug 27, 2018 for $549,000, according to the county's recorded deed.

What schools serve 21 Harbor Ave, Islip, NY?

21 Harbor Ave, Islip, NY is assigned to Islip Middle School (middle), rated C+; Islip High School (high), rated B+; Wing Elementary School (elementary). All sit in Islip Union Free School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21 Harbor Ave, Islip, NY compare to other homes in Islip 11751?

Among the 4,166 homes in Islip 11751, it is worth more than 81% of them ($813,542 against a typical $641,189) and its lot is bigger than 16% of them (0.17 ac against a typical 0.24 ac). Measured against all of Suffolk County, it is worth more than 67% of homes there. These shares are recounted nightly from the full county assessor record for each area, not from active listings.

More homes on Harbor Ave

Closest homes

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Assigned schools

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See this home in context

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