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Single Family ResidenceResidential
$1,070,016$510 / 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
Last sold for $520,000 on Jul 24, 2013

21728 LOST RIVER DR

DIAMOND BAR, CA 91765
4
Beds
3
Baths
2,098 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.
0.22 ac
Lot SizeThe size of the land the home sits on, from county records.
1963
Year BuiltThe year the home was originally built, according to county records.
1
StoriesHow many floors the home has above ground.
7
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.

Valuation

$1.1M
$1M low$1.1M high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$520,000 · Jul 24, 2013

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$12,516 (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.$1,011,216 (2026)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$506,147
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$505,069
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$991,390

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.23 in
30-Year Flood ChanceThe chance of at least one serious flood here in the next 30 years, not in any single year.30%
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
StyleThe architectural style of the home, such as ranch or colonial.Conventional
CountyLOS ANGELES
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.2010
Lot (acres)The size of the land the home sits on, from county records.0.22
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
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.No

Transaction History(7)

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
Evergreen Elementary SchoolA+
Elementary · Grades KG–5 · 0.1 mi
H
Diamond Bar High SchoolA+
High · Grades 9–12 · 0.4 mi
M
Chaparral Middle SchoolA+
Middle · Grades 6–8 · 1.3 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%

Owner Tools

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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

21728 Lost River Dr 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 70% of homes in Los Angeles County
  • Bigger than 72% of homes in Los Angeles County
  • Has a bigger lot than 69% of homes in Los Angeles County
  • Older than 92% 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
$360K$3.1M

This home is worth more than 57% 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$1,070,016
CheaperTypical $994,720Pricier

Pricier than 57% of homes nearby

Price per ft²$510
CheaperTypical $533Pricier

Pricier than 39% of homes nearby

Living area2,098 ft²
SmallerTypical 1,822 ft²Bigger

Bigger than 63% of homes nearby

Lot size0.22 ac
SmallerTypical 0.25 acBigger

Bigger than 42% of homes nearby

Year built1963
OlderTypical 1979Newer

Newer than 8% of homes nearby

How 21728 Lost River Dr ranks against every home in each area.
MeasureThis homeDiamond Bar 91765Los Angeles County
Estimated valuepricier than$1,070,01657% of homes70% of homes
Price per ft²pricier than$51039% of homes37% of homes
Living areabigger than2,098 ft²63% of homes72% of homes
Lot sizebigger than0.22 ac42% of homes69% of homes
Year builtnewer than19638% of homes60% of homes

About 21728 Lost River Dr

How much is 21728 Lost River Dr, Diamond Bar, CA worth?

The TopHap Estimate for 21728 Lost River Dr, Diamond Bar, CA is $1,070,016 as of Jul 14, 2026. The likely range is $1,007,550 to $1,132,482. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21728 Lost River Dr, Diamond Bar, CA last sell?

21728 Lost River Dr, Diamond Bar, CA last sold on Jul 24, 2013 for $520,000, according to the county's recorded deed. TopHap holds 2 recorded sales for this parcel.

How big is 21728 Lost River Dr, Diamond Bar, CA?

21728 Lost River Dr, Diamond Bar, CA has 4 bedrooms, 3 bathrooms, 2,098 square feet of living space and a 0.22-acre lot.

When was 21728 Lost River Dr, Diamond Bar, CA built?

21728 Lost River Dr, Diamond Bar, CA was built in 1963, making it 63 years old. It is a conventional home. The building has 1 story.

What schools serve 21728 Lost River Dr, Diamond Bar, CA?

21728 Lost River Dr, Diamond Bar, CA is assigned to Evergreen Elementary School (elementary), rated A+; Diamond Bar High School (high), 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 21728 Lost River Dr, 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 57% of them ($1,070,016 against a typical $994,720), its price per square foot is higher than 39% of them ($510 against a typical $533), it is bigger than 63% of them (2,098 ft² against a typical 1,822 ft²), its lot is bigger than 42% of them (0.22 ac against a typical 0.25 ac) and it is newer than 8% of them (1963 against a typical 1979). Measured against all of Los Angeles County, it is worth more than 70% 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 21728 Lost River Dr, Diamond Bar, CA?

The 2025 property tax bill for 21728 Lost River Dr, Diamond Bar, CA was $12,516. The county assessed it at $1,011,216.

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