Los Angeles County property record for 421 S Rock River Rd, Diamond Bar, CA 91765
| Property Type | Single Family Home |
|---|---|
| Details | 4 bd · 2 ba · 1,476 sqft · built 1971 |
| Lot Size | 0.165 acres (7,182 sqft) |
| Owner | Individual Name on File |
| Last Sale | $472,500 (Dec 2014) |
| Tax Bill | $7,881 (2025) |
| Deeds & Mortgages | Nov 2020 Mortgage |
| Flood Zone | Zone X (minimal risk) |
| APN | 8718-028-008 |
| Primary APN | 8718-028-008 |
|---|
| Bedrooms | 4 Beds |
|---|---|
| Full Baths | 2 Baths |
| Total Rooms | 10 Rooms |
| Stories | 1 Story |
| Building Area | 1,476 sqft Living Area |
| Fireplaces | 1 Fireplace |
| Fireplace | Fireplace |
| Year Built | Built 1971 |
|---|---|
| Effective Year Built | Effective 1971 |
| Architectural Style | Conventional |
| Exterior Material | Stucco |
| Construction Type | Wood |
| Roof Type | Hip |
| Roof Material | Wood Shingle |
| Lot Area | 7,182 sqft (0.165 acres) |
| Lot Dimensions | 123 ft deep x 61 ft wide |
| Garage Type | Detached |
| Cooling System | Wall Unit |
|---|---|
| Heating System | Central |
| Water Source | Commercial |
| Street Address | 421 S ROCK RIVER RD |
|---|---|
| City | DIAMOND BAR |
| State | CA |
| Zip | 91765-1562 |
| Property Category | Residential |
| Property Type | Residential > Single Family > Home |
| Local Zoning Code | LCR18000* |
| Legal Description | TRACT NO 28058 LOT 42 |
| Legal Subdivision | 28058 |
| Legal Tract | 28058 |
| Legal Block | 1 |
| Legal Lot Number | 42 |
| Jurisdiction | LOS ANGELES CA |
| Township / Civil Division | EAST SAN GABRIEL VALLEY |
| Census Block Group | 1 |
| Census Block | 1019 |
| Census Tract | 403327 |
421 S Rock River Rd is owned and occupied by an individual who bought it in December 2014.
Source: Los Angeles County records, as of August 25, 2026
| Owner of Record | Individual Name on File |
|---|---|
| Mailing Address | 421 S ROCK RIVER RD, DIAMOND BAR, CA 91765-1562 |
| Occupancy | Owner Occupied |
| Owner Type | Individual |
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 | Name on Deed |
|---|---|
| Last Sale | Dec 31, 2014 · Amount on File |
| Deed Sale | Dec 31, 2014 · Amount on File |
| Prior Sale | Aug 15, 2003 · Amount on File |
| Deed Document Number | 20141427924 |
| Prior Transfer Date | Mar 21, 2003 |
| Prior Transfer Doc | 0000861505 |
| Record Updated | Oct 29, 2026 |
| Document Type | Deed of Trust |
|---|---|
| Jurisdiction | LOS ANGELES CA |
| Property Address | 421 S ROCK RIVER RD, DIAMOND BAR, CA 91765-1562 |
| Transaction Type | Mortgage |
| Record Updated | Feb 5, 2021 |
| Title Company | STEWART TITLE OF CA INC |
| Name | Verified Name |
|---|---|
| Address | 1716 ARCDALE AVE, ROWLAND HEIGHTS, CA 91748-3107 |
| Document Number | 0001516630 |
|---|---|
| Date | Nov 24, 2020 |
| Instrument | 20-1516630 |
| Name | R M K FINANCIAL CORP |
|---|---|
| Type | Mortgage Company |
| Address | ONTARIO, CA 91761 |
| Type | Conventional Mortgage |
|---|---|
| Amount | Amount on Record |
| Term | 361 Months |
| Due | Dec 1, 2050 |
The 2025 property tax bill for 421 S Rock River Rd was $7,881.
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 | Pomona Unified School District (KG - 12) |
| Year | Tax Bill | Assessed Value |
|---|---|---|
| 2026 | $579,221 (+2%) Land $463,380 Building $115,841 | |
| 2025 | $7,881.00 | $567,865 Land $454,295 Building $113,570 |
| 2023 | $7,120.00 (+1.57%) | $545,816 Land $436,655 Building $109,161 |
| 2022 | $7,010.00 |
Assessed value is set for property tax purposes and is not a market price estimate.
FEMA maps place 421 S Rock River Rd 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 421 S Rock River Rd is low, with a 0.06% annual chance of wildfire.
Source: USDA Forest Service Wildfire Risk to Communities (2nd edition), as of 2024
| Wildfire Risk | Low lower than 63% of the US · lower than 78% of California |
|---|---|
| Wildfire Likelihood | 0.06% 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 69 locations within half a mile, as of December 31, 2025
| Provider | Max Down / Up (Mbps) |
|---|---|
| Spectrum Cable | 1,000 / 35 |
| Starlink Satellite | 280 / 30 |
| T-Mobile Fixed Wireless | 100 / 20 |
May also be available: AT&T, Verizon.
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