Skip to content
Skip to content
TopHapOpen in map
Single Family ResidenceResidential
$9,999,999$1,735 / 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 85How 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 $9,000,000 on Jan 28, 2019

21 MARYMONT AVE

ATHERTON, CA 94027
5
Beds
4.5
Baths
5,765 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.
0.86 ac
Lot SizeThe size of the land the home sits on, from county records.
2005
Year BuiltThe year the home was originally built, according to county records.
2
StoriesHow many floors the home has above ground.
12
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.
3
ParkingThe number of parking spaces on the property, including the garage.

Valuation

$10M
$10M low$10M high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$9,000,000 · Jan 28, 2019

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$111,265 (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.$10,240,458 (2026)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$7,168,323
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$3,072,135
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$10,039,666
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$8,018,190

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
CountySAN MATEO
Lot (acres)The size of the land the home sits on, from county records.0.86
HeatingThe type of heating system in the home.Central
CoolingThe type of cooling or air conditioning in the home.Central
PoolWhether the property has a pool, and what kind, such as in-ground.Yes

Transaction History(6)

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.

H
Woodside High SchoolB+
High · Grades 9–12 · 0.5 mi
E
Las Lomitas Elementary SchoolA+
Elementary · Grades KG–3 · 0.8 mi
M
La Entrada SchoolA+
Middle · Grades 4–8 · 1.8 mi

District: Las Lomitas Elementary School District

Neighborhood · ZIP 94027These 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.98
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.93
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.511

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.87%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.28%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.4.5%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.0.9%
PopulationHow many people live in this area.7,126
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.1,411 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$294,375
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$482,221
Average tempThe average temperature here across a full year.59°F
Annual precipHow much rain and melted snow falls here in a typical year.20 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.66%

Owner Tools

Do you own this home?
Claim this home

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 Marymont 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.

  • Among the most valuable homes in West Atherton
  • Costs more per square foot than 94% of homes in San Mateo County
  • Bigger than 98% of homes in San Mateo County
  • Has a bigger lot than 87% of homes in San Mateo County
  • Newer than 95% of homes in San Mateo County

What homes are worth in Atherton 94027

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

This home
$2.6M$10M

This home is worth more than almost all homes in Atherton 94027.

How it measures up in Atherton 94027

The dot is this home. The mark in the middle is the typical home in Atherton 94027.

Estimated value$9,999,999
CheaperTypical $9,049,575Pricier

Pricier than almost all homes nearby

Price per ft²$1735
CheaperTypical $1982Pricier

Pricier than 34% of homes nearby

Living area5,765 ft²
SmallerTypical 3,930 ft²Bigger

Bigger than 72% of homes nearby

Lot size0.86 ac
SmallerTypical 1 acBigger

Bigger than 28% of homes nearby

Year built2005
OlderTypical 1958Newer

Newer than 82% of homes nearby

How 21 Marymont Ave ranks against every home in each area.
MeasureThis homeWest AthertonAtherton 94027San Mateo County
Estimated valuepricier than$9,999,999almost all homesalmost all homesalmost all homes
Price per ft²pricier than$173534% of homes34% of homes94% of homes
Living areabigger than5,765 ft²62% of homes72% of homes98% of homes
Lot sizebigger than0.86 ac25% of homes28% of homes87% of homes
Year builtnewer than200578% of homes82% of homes95% of homes

About 21 Marymont Ave

How much is 21 Marymont Ave, Atherton, CA worth?

The TopHap Estimate for 21 Marymont Ave, Atherton, CA is $9,999,999 as of Sep 24, 2026. The likely range is $9,999,999 to $9,999,999. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21 Marymont Ave, Atherton, CA last sell?

21 Marymont Ave, Atherton, CA last sold on Jan 28, 2019 for $9,000,000, according to the county's recorded deed. TopHap holds 3 recorded sales for this parcel.

How big is 21 Marymont Ave, Atherton, CA?

21 Marymont Ave, Atherton, CA has 5 bedrooms, 4.5 bathrooms, 5,765 square feet of living space and a 0.86-acre lot.

When was 21 Marymont Ave, Atherton, CA built?

21 Marymont Ave, Atherton, CA was built in 2005, making it 21 years old. The building has 2 stories.

What schools serve 21 Marymont Ave, Atherton, CA?

21 Marymont Ave, Atherton, CA is assigned to Woodside High School (high), rated B+; Las Lomitas Elementary School (elementary), rated A+; La Entrada School (middle), rated A+. All sit in Las Lomitas Elementary School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21 Marymont Ave, Atherton, CA compare to other homes in Atherton 94027?

Among the 2,583 homes in Atherton 94027, it is worth more than almost all of them ($9,999,999 against a typical $9,049,575), its price per square foot is higher than 34% of them ($1735 against a typical $1982), it is bigger than 72% of them (5,765 ft² against a typical 3,930 ft²), its lot is bigger than 28% of them (0.86 ac against a typical 1 ac) and it is newer than 82% of them (2005 against a typical 1958). Measured against all of San Mateo County, it is worth more than almost all 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 Marymont Ave, Atherton, CA?

The 2025 property tax bill for 21 Marymont Ave, Atherton, CA was $111,265. The county assessed it at $10,240,458.

More homes on Marymont Ave

Closest homes

More homes in Atherton 94027

Assigned schools

Explore the area

See this home in context

Open 21 Marymont Ave on TopHap’s interactive map to compare it against every sale nearby, overlay school zones and flood risk, and run a CMA.

Open in map
A flyover of TopHap's photorealistic 3D map, with recorded sale prices pinned to homes
Search any address, city, zip, or county…3D$1.9M$6.25MOpen in map