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Single Family ResidenceResidential
$822,252$843 / 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 $750,000 on Oct 19, 2022

21 CASTRO ST

FOREST KNOLLS, CA 94933
3
Beds
1
Baths
975 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.
0.11 ac
Lot SizeThe size of the land the home sits on, from county records.
1924
Year BuiltThe year the home was originally built, according to county records.

Valuation

$822K
$765K low$879K high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$750,000 · Oct 19, 2022

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$10,381 (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.$795,900 (2026)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$424,480
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$371,420
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$780,300

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.86 in
30-Year Flood ChanceThe chance of at least one serious flood here in the next 30 years, not in any single year.51%
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.1 percent flood zone

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
StyleThe architectural style of the home, such as ranch or colonial.Contemporary
CountyMARIN
Effective Year BuiltAn adjusted build year that accounts for condition and major remodels. A big renovation can make a home count as newer than it is.1935
Lot (acres)The size of the land the home sits on, from county records.0.12
HeatingThe type of heating system in the home.Central
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 · 150 ft²Patio · 150 ft²

Transaction History(4)

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.

E
Lagunitas Elementary SchoolB+
Elementary · Grades KG–8 · 0.8 mi
H
Archie Williams High SchoolA+
High · Grades 9–12 · 6.8 mi

District: Tamalpais Union High School District

Neighborhood · ZIP 94933These 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.142
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.82
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.466

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.95%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.31%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.9.4%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.1.3%
PopulationHow many people live in this area.271
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.440 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$112,150
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$122,546
Average tempThe average temperature here across a full year.59°F
Annual precipHow much rain and melted snow falls here in a typical year.39 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.78%

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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 Castro St 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 less than 84% of homes in Marin County
  • Costs more per square foot than 84% of homes in Forest Knolls 94933
  • Smaller than 92% of homes in Marin County
  • Has a smaller lot than 92% of homes in Forest Knolls 94933
  • Older than 92% of homes in Marin County

What homes are worth in Forest Knolls 94933

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

This home
$342K$1.9M

This home is worth more than 42% of homes in Forest Knolls 94933.

How it measures up in Forest Knolls 94933

The dot is this home. The mark in the middle is the typical home in Forest Knolls 94933.

Estimated value$822,252
CheaperTypical $883,697Pricier

Pricier than 42% of homes nearby

Price per ft²$843
CheaperTypical $636Pricier

Pricier than 84% of homes nearby

Living area975 ft²
SmallerTypical 1,446 ft²Bigger

Bigger than 20% of homes nearby

Lot size0.11 ac
SmallerTypical 0.33 acBigger

Bigger than 8% of homes nearby

Year built1924
OlderTypical 1930Newer

Newer than 35% of homes nearby

How 21 Castro St ranks against every home in each area.
MeasureThis homeForest Knolls 94933Marin County
Estimated valuepricier than$822,25242% of homes16% of homes
Price per ft²pricier than$84384% of homes58% of homes
Living areabigger than975 ft²20% of homes8% of homes
Lot sizebigger than0.11 ac8% of homes23% of homes
Year builtnewer than192435% of homes8% of homes

About 21 Castro St

How much is 21 Castro St, Forest Knolls, CA worth?

The TopHap Estimate for 21 Castro St, Forest Knolls, CA is $822,252 as of Aug 30, 2026. The likely range is $765,144 to $879,360. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21 Castro St, Forest Knolls, CA last sell?

21 Castro St, Forest Knolls, CA last sold on Oct 19, 2022 for $750,000, according to the county's recorded deed. TopHap holds 3 recorded sales for this parcel.

How big is 21 Castro St, Forest Knolls, CA?

21 Castro St, Forest Knolls, CA has 3 bedrooms, 1 bathrooms, 975 square feet of living space and a 0.12-acre lot.

When was 21 Castro St, Forest Knolls, CA built?

21 Castro St, Forest Knolls, CA was built in 1924, making it 102 years old. It is a contemporary home.

What schools serve 21 Castro St, Forest Knolls, CA?

21 Castro St, Forest Knolls, CA is assigned to Lagunitas Elementary School (elementary), rated B+; Archie Williams High School (high), rated A+. All sit in Tamalpais Union High School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21 Castro St, Forest Knolls, CA compare to other homes in Forest Knolls 94933?

Among the 306 homes in Forest Knolls 94933, it is worth more than 42% of them ($822,252 against a typical $883,697), its price per square foot is higher than 84% of them ($843 against a typical $636), it is bigger than 20% of them (975 ft² against a typical 1,446 ft²), its lot is bigger than 8% of them (0.11 ac against a typical 0.33 ac) and it is newer than 35% of them (1924 against a typical 1930). Measured against all of Marin County, it is worth more than 16% 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 Castro St, Forest Knolls, CA?

The 2025 property tax bill for 21 Castro St, Forest Knolls, CA was $10,381. The county assessed it at $795,900.

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