Los Angeles County property record for 21720 Lost River Dr, Diamond Bar, CA 91765
| Property Type | Single Family Home |
|---|---|
| Details | 4 bd · 2 ba · 1,288 sqft · built 1963 |
| Lot Size | 0.208 acres (9,077 sqft) |
| Owner | 2 Individual Names on File |
| Last Sale | $652,000 (Jun 2017) |
| Tax Bill | $9,646 (2025) |
| Deeds & Mortgages | Jun 2017 Sale |
| Flood Zone | Zone X (minimal risk) |
| APN | 8285-004-003 |
| Primary APN | 8285-004-003 |
|---|
| Bedrooms | 4 Beds |
|---|---|
| Full Baths | 2 Baths |
| Total Rooms | 9 Rooms |
| Stories | 1 Story |
| Building Area | 1,288 sqft Living Area |
| Fireplaces | 1 Fireplace |
| Fireplace | Fireplace |
| Year Built | Built 1963 |
|---|---|
| Effective Year Built | Effective 1963 |
| Architectural Style | Conventional |
| Exterior Material | Stucco |
| Construction Type | Wood |
| Roof Type | Hip |
| Roof Material | Wood Shingle |
| Lot Area | 9,077 sqft (0.208 acres) |
| Lot Dimensions | 124 ft deep x 73 ft wide |
| Cooling System | Central |
|---|---|
| Heating System | Central |
| Street Address | 21720 LOST RIVER DR |
|---|---|
| City | DIAMOND BAR |
| State | CA |
| Zip | 91765-3129 |
| Property Category | Residential |
| Property Type | Residential > Single Family > Home |
| Local Zoning Code | LCR17500* |
| Legal Description | TRACT NO 25987 LOT 103 |
| Legal Subdivision | 25987 |
| Legal Tract | 25987 |
| Legal Block | 1 |
| Legal Lot Number | 103 |
| Jurisdiction | LOS ANGELES CA |
| Township / Civil Division | EAST SAN GABRIEL VALLEY |
| Census Block Group | 1 |
| Census Block | 1002 |
| Census Tract | 403325 |
21720 Lost River Dr is owned and occupied by two individuals who bought it in June 2017.
Source: Los Angeles County records, as of August 25, 2026
| Owner of Record | 2 Individual Names on File |
|---|---|
| Mailing Address | 21720 LOST RIVER DR, DIAMOND BAR, CA 91765-3129 |
| Occupancy | Owner Occupied |
| Owner Type | Individual |
| Vesting | Joint Tenants |
Owner names and exact recorded amounts are on file and can be viewed instantly on this page with a free 10-day trial.
| Deed Names | 2 Names on Deed |
|---|---|
| Last Sale | Jun 16, 2017 · Amount on File |
| Deed Sale | Jun 16, 2017 · Amount on File |
| Prior Sale | Apr 5, 2005 · Amount on File |
| Deed Document Number | 2017669124 |
| Prior Transfer Date | Mar 25, 2005 |
| Prior Transfer Doc | 0000779340 |
| Record Updated | Oct 29, 2026 |
| Document Type | Grant Deed |
|---|---|
| Jurisdiction | LOS ANGELES CA |
| Recording Date | Jun 16, 2017 |
| Property Address | 21720 LOST RIVER DR, DIAMOND BAR, CA 91765-3129 |
| Document Number | 0000669124 |
| Instrument Date | Jun 12, 2017 |
| Instrument | 669124 |
| Transaction Type | Transfer |
| Record Updated | Jun 20, 2017 |
| Title Company | US ESCROW INC |
| Amount | Amount on Record |
|---|---|
| Tax | $717.00 |
| Amount Accuracy | Full Value |
| Additional |
|
| Name | Verified Name |
|---|
| Name | Verified Name |
|---|---|
| Relationship | Joint Tenants with Right of Survivorship |
| Address | 21720 LOST RIVER DR DIAMOND BAR CA 917653129, DIAMOND BAR, CA 91765-3129 |
The 2025 property tax bill for 21720 Lost River Dr was $9,646.
Source: Los Angeles County assessment roll, as of August 25, 2026
| Type | Name |
|---|---|
| State | California |
| County | Los Angeles County |
| Municipality | Diamond Bar City |
| Unified School District | Walnut Valley Unified School District (KG - 12) |
| Year | Tax Bill | Assessed Value |
|---|---|---|
| 2026 | $771,828 (+2%) Land $579,820 Building $192,008 | |
| 2025 | $9,646.00 | $756,695 Land $568,451 Building $188,244 |
| 2023 | $9,030.00 (+2.1%) | $727,313 Land $546,378 Building $180,935 |
| 2022 | $8,844.00 |
Assessed value is set for property tax purposes and is not a market price estimate.
FEMA maps place 21720 Lost River Dr in Zone X, an area of minimal flood risk.
Source: FEMA National Flood Hazard Layer, effective September 30, 2026
| FEMA Flood Zone | Zone X minimal risk |
|---|---|
| Flood Insurance Requirement | Not required lenders may require it |
Values are read at the parcel center point; lenders make the official flood determination.
Wildfire risk around 21720 Lost River Dr is low, with a 0.02% annual chance of wildfire.
Source: USDA Forest Service Wildfire Risk to Communities (2nd edition), as of 2024
| Wildfire Risk | Low lower than 80% of the US · lower than 88% of California |
|---|---|
| Wildfire Likelihood | 0.02% annual chance |
| Exposure | None beyond ember reach |
Values cover an area roughly 900 ft across, not the parcel itself; insurers use their own ratings.
Source: EPA Safe Drinking Water Information System, as of September 2026
| Water System | WALNUT VALLEY WATER DISTRICT serves 100,941 people · EPA ID CA1910234 |
|---|---|
| Water Source | Purchased surface water from several systems |
| Last State Inspection | Jun 2023 |
| Lead | Under 1 ppb (2022–2024) action level 15 ppb |
| Water Quality | None last 10 years |
|---|---|
| Treatment and Procedure | None last 10 years |
| Monitoring and Reporting | None last 3 years |
Results are for the whole water system, not water tested at this address; lead at the tap also depends on the building's own pipes.
Source: FCC Broadband Data Collection, based on 437 locations within half a mile, as of December 31, 2025
| Provider | Max Down / Up (Mbps) |
|---|---|
| Frontier Fiber | 7,000 / 7,000 |
| Spectrum Cable | 1,000 / 35 |
| AT&T Fixed Wireless | 100 / 20 |
| T-Mobile Fixed Wireless | 100 / 20 |
May also be available: GeoLinks, Verizon.
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