Contra Costa County property record for 4121 S Castro St, Martinez, CA 94553
| Property Type | Single Family Home |
|---|---|
| Details | 2 bd · 1 ba · 816 sqft · built 1951 |
| Lot Size | 0.21 acres (9,147 sqft) |
| Owner | 2 Trust Names on File |
| Tax Bill | $3,773 (2025) |
| Deeds & Mortgages | Apr 2026 Sale |
| Flood Zone | Zone AO (high risk) |
| APN | 370-291-012 |
| Primary APN | 370-291-012 |
|---|---|
| Alternative APN |
|
| Bedrooms | 2 Beds |
|---|---|
| Full Baths | 1 Bath |
| Total Rooms | 4 Rooms |
| Stories | 1 Story |
| Building Area | 816 sqft Living Area |
| 1st Floor Area | 816 sqft |
| Year Built | Built 1951 |
|---|---|
| Effective Year Built | Effective 1951 |
| Lot Area | 9,147 sqft (0.21 acres) |
| Garage Type | Attached |
| Garage Area | 240 sqft |
| Parking Spaces | 1 Parking Space |
| Street Address | 4121 S CASTRO ST |
|---|---|
| City | MARTINEZ |
| State | CA |
| Zip | 94553-3951 |
| Property Category | Residential |
| Property Type | Residential > Single Family > Home |
| Local Zoning Code | R1 |
| Legal Description | POR RO EL PINOLE |
| Legal Subdivision | EL PINOLE RHO |
| Jurisdiction | CONTRA COSTA CA |
| Township / Civil Division | CENTRAL CONTRA COSTA |
| Census Block Group | 3 |
| Census Block | 3017 |
| Census Tract | 318000 |
4121 S Castro St is owner-occupied and held in a trust since November 2001.
Source: Contra Costa County records, as of July 14, 2026
Owner names and exact recorded amounts are on file and can be viewed instantly on this page with a free 10-day trial.
| Owner of Record | 2 Trust Names on File |
|---|---|
| Mailing Address | 4121 S CASTRO ST, MARTINEZ, CA 94553-3951 |
| Occupancy | Owner Occupied |
| Owner Type | Company |
| Vesting | Trust |
| Deed Names | 2 Names on Deed |
|---|---|
| Last Transfer Date | Nov 27, 2001 |
| Transfer Doc | 0000376069 |
| Record Updated | Sep 20, 2026 |
| Document Type | Grant Deed |
|---|---|
| Jurisdiction | CONTRA COSTA CA |
| Recording Date | Apr 15, 2026 |
| Property Address | 4121 S CASTRO ST, MARTINEZ, CA 94553-3951 |
| Document Number | 0000037688 |
| Instrument Date | Apr 10, 2026 |
| Instrument | 202637688 |
| Transaction Type | Transfer |
| Record Updated | Jul 12, 2026 |
| Title Company | NONE LISTED ON DOCUMENT |
| Tax | $0.00 |
|---|---|
| Amount Accuracy | Full Amount Stated |
| Additional |
|
| Name | Verified Name |
|---|
| Name | Verified Name |
|---|---|
| Relationship | Trust |
| Address | 4121 S CASTRO ST, MARTINEZ, CA 94553-3951 |
The 2025 property tax bill for 4121 S Castro St was $3,773.
Source: Contra Costa County assessment roll, as of July 14, 2026
| Type | Name |
|---|---|
| State | California |
| County | Contra Costa County |
| Municipality | Martinez City |
| Unified School District | Martinez Unified School District (KG - 12) |
| Year | Tax Bill | Assessed Value |
|---|---|---|
| 2026 | $250,809 (+2%) Land $117,563 Building $133,246 | |
| 2025 | $3,773.00 Homeowner's exemption | $245,892 Land $115,258 Building $130,634 |
| 2023 | $3,542.00 (+1.58%) Homeowner's exemption | $236,346 Land $110,784 Building $125,562 |
| 2022 | $3,487.00 |
Assessed value is set for property tax purposes and is not a market price estimate.
FEMA maps place 4121 S Castro St in Zone AO, a high-risk flood area; flood insurance is required for federally backed loans.
Source: FEMA National Flood Hazard Layer, effective October 12, 2026 · OpenFEMA NFIP redacted claims and policies, as of September 2026
| FEMA Flood Zone | Zone AO high risk · sheet flow 1–3 ft |
|---|---|
| 100-Year Floodplain | Yes 1% annual chance |
| Floodway | No |
| Base Flood Elevation | Varies along the reach; see FIRM |
| Flood Insurance Requirement | Required federally backed loans |
| Flood Insurance Cost | Premium on File median of 109 policies |
| Nearby Flood Policies | 109 in force |
| Nearby Flood Claims | 32 (1980–2019) |
| Claims Outside the SFHA | 3 of 32 |
| Most Recent Claim | Feb 2019 |
| Claims by Event |
|
Values are read at the parcel center point; flood claims are located to the census block group, not this parcel; lenders make the official flood determination.
Wildfire risk around 4121 S Castro St is moderate, ranking above 43% of the US, with a 0.07% annual chance of wildfire.
Source: USDA Forest Service Wildfire Risk to Communities (2nd edition), as of 2024
| Wildfire Risk | Moderate above 43% of the US · lower than 74% of California |
|---|---|
| Wildfire Likelihood | 0.07% annual chance |
| Exposure | Indirect within ember reach |
| Adjoins Burnable Land | Yes |
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 | CITY OF MARTINEZ serves 31,015 people · EPA ID CA0710006 |
|---|---|
| Water Source | Purchased surface water from CONTRA COSTA WATER DISTRICT |
| Last State Inspection | Oct 2025 |
| Lead | Under 1 ppb (2023–2025) 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 212 locations within half a mile, as of December 31, 2025
| Provider | Max Down / Up (Mbps) |
|---|---|
| Xfinity Cable | 2,000 / 250 |
| AT&T Fixed Wireless · DSL | 100 / 20 |
May also be available: Astound Broadband, T-Mobile, Unwired, Verizon.
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