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Single Family ResidenceResidential
$1,139,292$488 / 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 94How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Jul 14, 2026

21427 RUNNING RIVER CT

DIAMOND BAR, CA 91765
4
Beds
3
Baths
2,334 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.
0.19 ac
Lot SizeThe size of the land the home sits on, from county records.
1977
Year BuiltThe year the home was originally built, according to county records.
2
StoriesHow many floors the home has above ground.
13
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.

Valuation

$1.1M
$1.1M low$1.2M high
Est. Owner EquityRoughly how much of the home's value the owner would keep after paying off known loans. It is our estimate minus the loans still owed.$1,039,292
Est. Lendable EquityThe part of the owner's equity a lender would typically let them borrow against — about 80% of their equity.$831,434
Loan-to-ValueHow much is still owed on the home compared to what it is worth. 80% means loans equal 80% of our estimate, so it shifts when the estimate does.9%
1st MortgageA loan still believed to be open on this home, in the order lenders get repaid. The first position is paid back before the second.$100,000
WASHINGTON MUTUAL FSB · recorded Apr 15, 2002

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$5,198 (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.$374,820 (2025)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$83,735
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$291,085
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$367,472

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.Conventional
CountyLOS ANGELES
Lot (acres)The size of the land the home sits on, from county records.0.19
ConstructionThe main material the home's frame and walls are built from.Wood (Unspecified)
RoofThe main material covering the roof, such as asphalt shingle or tile.Wood Shingle
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.Yes

Transaction History(2)

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
Diamond Bar High SchoolA+
High · Grades 9–12 · 0.5 mi
E
Evergreen Elementary SchoolA+
Elementary · Grades KG–5 · 0.7 mi
M
Chaparral Middle SchoolA+
Middle · Grades 6–8 · 1.2 mi

District: Walnut Valley Unified School District

Neighborhood · ZIP 91765These 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.46
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.101
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.388

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.35%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.9.2%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.1.7%
PopulationHow many people live in this area.41,302
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.2,738 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$98,979
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$125,933
Average tempThe average temperature here across a full year.63°F
Annual precipHow much rain and melted snow falls here in a typical year.19 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.73%

Ownership

OccupancyWhether the owner appears to live here or somewhere else. It is inferred from the mailing address on record.Owner occupied
Company ownedWhether the owner is a company or trust rather than a person.Yes

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

21427 Running River Ct 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 72% of homes in Los Angeles County
  • Costs less per square foot than 73% of homes in Diamond Bar 91765
  • Bigger than 79% of homes in Los Angeles County
  • Has a smaller lot than 75% of homes in Diamond Bar 91765
  • Newer than 73% of homes in Los Angeles County

What homes are worth in Diamond Bar 91765

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

This home
$359K$3.1M

This home is worth more than 64% of homes in Diamond Bar 91765.

How it measures up in Diamond Bar 91765

The dot is this home. The mark in the middle is the typical home in Diamond Bar 91765.

Estimated value$1,139,292
CheaperTypical $984,599Pricier

Pricier than 64% of homes nearby

Price per ft²$488
CheaperTypical $537Pricier

Pricier than 27% of homes nearby

Living area2,334 ft²
SmallerTypical 1,813 ft²Bigger

Bigger than 75% of homes nearby

Lot size0.19 ac
SmallerTypical 0.25 acBigger

Bigger than 25% of homes nearby

Year built1977
OlderTypical 1979Newer

Newer than 43% of homes nearby

How 21427 Running River Ct ranks against every home in each area.
MeasureThis homeDiamond Bar 91765Los Angeles County
Estimated valuepricier than$1,139,29264% of homes72% of homes
Price per ft²pricier than$48827% of homes30% of homes
Living areabigger than2,334 ft²75% of homes79% of homes
Lot sizebigger than0.19 ac25% of homes61% of homes
Year builtnewer than197743% of homes73% of homes

About 21427 Running River Ct

How much is 21427 Running River Ct, Diamond Bar, CA worth?

The TopHap Estimate for 21427 Running River Ct, Diamond Bar, CA is $1,139,292 as of Jul 14, 2026. The likely range is $1,074,579 to $1,204,005. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21427 Running River Ct, Diamond Bar, CA last sell?

21427 Running River Ct, Diamond Bar, CA last sold on Jan 1, 1900, according to the county's recorded deed.

How big is 21427 Running River Ct, Diamond Bar, CA?

21427 Running River Ct, Diamond Bar, CA has 4 bedrooms, 3 bathrooms, 2,334 square feet of living space and a 0.19-acre lot.

When was 21427 Running River Ct, Diamond Bar, CA built?

21427 Running River Ct, Diamond Bar, CA was built in 1977, making it 49 years old. It is a conventional home. The building has 2 stories.

What schools serve 21427 Running River Ct, Diamond Bar, CA?

21427 Running River Ct, Diamond Bar, CA is assigned to Diamond Bar High School (high), rated A+; Evergreen Elementary School (elementary), rated A+; Chaparral Middle School (middle), rated A+. All sit in Walnut Valley Unified School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21427 Running River Ct, Diamond Bar, CA compare to other homes in Diamond Bar 91765?

Among the 15,284 homes in Diamond Bar 91765, it is worth more than 64% of them ($1,139,292 against a typical $984,599), its price per square foot is higher than 27% of them ($488 against a typical $537), it is bigger than 75% of them (2,334 ft² against a typical 1,813 ft²), its lot is bigger than 25% of them (0.19 ac against a typical 0.25 ac) and it is newer than 43% of them (1977 against a typical 1979). Measured against all of Los Angeles County, it is worth more than 72% 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 21427 Running River Ct, Diamond Bar, CA?

The 2025 property tax bill for 21427 Running River Ct, Diamond Bar, CA was $5,198. The county assessed it at $374,820.

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