Blog · October 14, 2026 · California
Using the Antioch Plat Map
A recorded plat shows how land near Walnut Creek was divided into lots.
Main page: Contra Costa County, CA GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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When a listing near Walnut Creek mentions a lot number, the Antioch plat map is where those numbers come from. In this Antioch guide: where plats are filed, plat versus tax map, and what to look for on the sheet.
The Antioch plat map: start here
For land around Oakley, look for the plat book reference on the parcel record; bring that to the recorder's office or its online index.
The free map to start with
Go first to the Contra Costa County parcel viewer; it covers each assessed parcel from Pittsburg to Concord. For a tract near Clayton, put in a street address, an owner's name or a parcel number, and the viewer zooms to the match. On ground around Clayton, the record panel typically gives the owner of record, assessed acreage, the parcel number and often a sale date.
Contra Costa County in a few facts
Martinez serves as the county seat, home to the main records offices. Smaller places on the map include Brentwood, Oakley, Pittsburg, and Clayton, each with its own cluster of lots. About 1,155,025 people call Contra Costa County home (Census Bureau estimate, 2023) across some 717 square miles. Features like Clayton-Marsh Creek-Greenville Fault, San Pablo Dam Reservoir, and Mount Diablo State Park make handy reference points on the map near Brentwood.
Neighboring parcel maps
Contra Costa County meets Alameda County, Marin County, Sacramento County, San Francisco County, and San Joaquin County; every one of them runs a separate parcel map. Acreage along the edge near Oakley can show up across two assessors' files, so look at the adjacent map as well. On ground around Pittsburg, our state page links every bordering county map across California.
Reading the legal description
California uses the Public Land Survey System, so rural legal descriptions near Pittsburg cite section, township and range. Each section is nominally a mile square, about 640 acres, and a township holds 36 of them, though corrections make some sections near Brentwood odd-sized. Copy the legal description from the record for the parcel near Clayton for any title or survey request.
When a plat changes
Lots near Concord can be combined or reconfigured by a replat, so check for later filings; street vacations near Walnut Creek show up in the records too.
Where Antioch fits in
Antioch sits in Contra Costa County, California, so its parcels are on the county's map. On ground around Oakley, city or town hall handles matters such as zoning, permits and utilities inside its limits, and the county still keeps the parcel and deed records. Land beyond the town limits toward Walnut Creek often falls under county rules, not municipal ones.
How a plat differs from the tax map
Where lines don't match in Antioch, the recorded plat and a survey control.
Details on the Antioch plat map
For property near Pittsburg, the sheet usually includes lot and block numbers, dimensions and bearings, street rights-of-way and easements.
Online indexes and office visits
For property near Oakley, some counties put plat images online, while others require a visit or a request; small fees are common.
On site with the map
Most viewers work in a phone browser, which helps when you're standing on land near Oakley, but coverage can be spotty out of town. A screenshot of the parcel near Brentwood with its ID helps when you meet an owner or agent.
Deeds, plats and who keeps them
The map is an index, not the title: deeds, subdivision plats and easements covering ground around Pittsburg are filed with the County Recorder. Out toward Concord, have ready the book and page from the tax record so staff can find the deed fast.
Limits of the parcel data
The acreage figure is a tax-roll number; only a licensed surveyor sets the real boundary for a parcel near Pittsburg. For a parcel near Oakley, records update in batches, so a deed recorded last month might lag behind.
Getting answers from the right desk
Questions about value or the owner field for land near Pittsburg go to the County Assessor, the office behind the parcel record. Building or septic questions for a lot near Clayton need the planning or permitting office, depending on whether the land is inside town limits.
When there's no plat
Rural land near Pittsburg that was never subdivided may have no plat at all; the deed and any recorded survey describe it instead.
Frequently asked
What is a replat in Antioch?
Usually, combining or splitting lots near Walnut Creek usually needs a recorded plat change, often with a surveyor's drawing.
Is a plat map a survey in Antioch?
For property near Walnut Creek, a recorded plat is based on a survey, but the GIS map is not; trust the plat when they differ.
What is a lot and block description near Walnut Creek?
Good question; it points to a spot on the plat for that subdivision near Clayton.
Where can I find the Antioch plat map?
Usually, recorded plats near Concord are filed with the County Recorder; small copy fees are common.
What's the tax parcel number used for near Walnut Creek?
The parcel ID identifies one tax parcel near Brentwood, and it's on the record panel and tax bills.
Open the official Contra Costa County, CA parcel map See it in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey, especially for fences, setbacks, or boundary disputes.