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Single Family ResidenceResidential
$793,365$538 / 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 Jul 14, 2026
Last sold for $472,500 on Dec 31, 2014

421 S ROCK RIVER RD

DIAMOND BAR, CA 91765
4
Beds
2
Baths
1,476 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.
0.16 ac
Lot SizeThe size of the land the home sits on, from county records.
1971
Year BuiltThe year the home was originally built, according to county records.
1
StoriesHow many floors the home has above ground.
10
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.

Valuation

$793K
$741K low$845K high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$472,500 · Dec 31, 2014
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.$458,365
Est. Lendable EquityThe part of the owner's equity a lender would typically let them borrow against — about 80% of their equity.$366,692
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.39%
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.$335,000
R M K FINANCIAL CORP · recorded Nov 24, 2020

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$7,881 (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.$567,865 (2025)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$454,295
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$113,570
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$556,732

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.0.17
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.Wall Unit
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, Detached
PoolWhether the property has a pool, and what kind, such as in-ground.Yes

Transaction History(3)

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
Armstrong Elementary SchoolC
Elementary · Grades KG–6 · 0.3 mi
M
Lorbeer Middle SchoolC+
Middle · Grades 7–8 · 0.6 mi
H
Diamond Ranch High SchoolA-
High · Grades 9–12 · 2.3 mi

District: Pomona 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.No

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

421 S Rock River Rd 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 73% of homes in Diamond Bar 91765
  • Smaller than 70% of homes in Diamond Bar 91765
  • Has a smaller lot than 90% of homes in Diamond Bar 91765
  • Older than 76% of homes in Diamond Bar 91765

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 27% 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$793,365
CheaperTypical $984,599Pricier

Pricier than 27% of homes nearby

Price per ft²$538
CheaperTypical $537Pricier

Pricier than 50% of homes nearby

Living area1,476 ft²
SmallerTypical 1,813 ft²Bigger

Bigger than 30% of homes nearby

Lot size0.16 ac
SmallerTypical 0.25 acBigger

Bigger than 10% of homes nearby

Year built1971
OlderTypical 1979Newer

Newer than 24% of homes nearby

How 421 S Rock River Rd ranks against every home in each area.
MeasureThis homeDiamond Bar 91765Los Angeles County
Estimated valuepricier than$793,36527% of homes46% of homes
Price per ft²pricier than$53850% of homes43% of homes
Living areabigger than1,476 ft²30% of homes43% of homes
Lot sizebigger than0.16 ac10% of homes48% of homes
Year builtnewer than197124% of homes67% of homes

About 421 S Rock River Rd

How much is 421 S Rock River Rd, Diamond Bar, CA worth?

The TopHap Estimate for 421 S Rock River Rd, Diamond Bar, CA is $793,365 as of Jul 14, 2026. The likely range is $741,418 to $845,312. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 421 S Rock River Rd, Diamond Bar, CA last sell?

421 S Rock River Rd, Diamond Bar, CA last sold on Dec 31, 2014 for $472,500, according to the county's recorded deed. TopHap holds 2 recorded sales for this parcel.

How big is 421 S Rock River Rd, Diamond Bar, CA?

421 S Rock River Rd, Diamond Bar, CA has 4 bedrooms, 2 bathrooms, 1,476 square feet of living space and a 0.17-acre lot.

When was 421 S Rock River Rd, Diamond Bar, CA built?

421 S Rock River Rd, Diamond Bar, CA was built in 1971, making it 55 years old. It is a conventional home. The building has 1 story.

What schools serve 421 S Rock River Rd, Diamond Bar, CA?

421 S Rock River Rd, Diamond Bar, CA is assigned to Armstrong Elementary School (elementary), rated C; Lorbeer Middle School (middle), rated C+; Diamond Ranch High School (high), rated A-. All sit in Pomona Unified School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 421 S Rock River Rd, 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 27% of them ($793,365 against a typical $984,599), its price per square foot is higher than 50% of them ($538 against a typical $537), it is bigger than 30% of them (1,476 ft² against a typical 1,813 ft²), its lot is bigger than 10% of them (0.16 ac against a typical 0.25 ac) and it is newer than 24% of them (1971 against a typical 1979). Measured against all of Los Angeles County, it is worth more than 46% 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 421 S Rock River Rd, Diamond Bar, CA?

The 2025 property tax bill for 421 S Rock River Rd, Diamond Bar, CA was $7,881. The county assessed it at $567,865.

More homes on S Rock River Rd

Closest homes

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Assigned schools

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