Blog · October 14, 2026 · California
Using the San Carlos Plat Map
Lots in San Carlos trace back to recorded plats filed with the county.
Main page: San Mateo County, CA GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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Checking easements on a house in San Carlos? Start with the San Carlos plat map, because the recorded plat shows how the land was divided. In this San Carlos guide: where to request a copy, plat versus tax map, and the details that matter to buyers.
The San Carlos plat map: start here
For a lot in San Carlos, the deed or parcel record often names the subdivision and plat reference; that makes the request quick.
The free map to start with
Your first stop is the San Mateo County parcel viewer; it covers every assessed parcel from San Mateo to Foster City. If you're looking near Foster City, enter a street address, an owner's name or a parcel number, then pick the result to center the map on it. On ground around Atherton, a pop-up or side panel typically gives the owner of record, acreage on the tax roll, a parcel ID and often a sale date.
A word on accuracy
Parcel lines are drawn for taxes, not measured on the ground, so a tree line near San Mateo may sit a few yards off the line on screen. On ground around Foster City, records update in batches, so a deed recorded last month might lag behind.
Places you'll see on the map
Redwood City serves as the county seat, where most land records are kept. You'll also find Belmont, Foster City, and Atherton, where town lots give way to larger tracts. Roughly 726,353 people live in San Mateo County (Census Bureau estimate, 2023) spread over about 449 square miles. Places such as Don Edwards San Francisco Bay National Wildlife Refuge are easy to spot when you zoom out from Woodside.
San Carlos, CA: the basics
San Carlos sits in San Mateo County, California, so its parcels are on the county's map. Local government in San Carlos handles matters such as zoning, permits and utilities for lots inside the boundary, but the county runs assessment and recording. Land beyond the town limits toward Atherton usually answers to county rules rather than the town's.
Replats and vacations
An amended plat may change lots around San Mateo, so check for later filings; vacated streets or alleys also get recorded.
Recorded plat or GIS layer
When the two disagree for a lot near Belmont, trust the recorded documents over the GIS layer.
Taking the map into the field
Most viewers work in a phone browser, useful out on a road near Woodside, though signal can drop in rural spots. A saved image of the lot near San Mateo and its lines is a good backup.
Reading the legal description
California follows the Public Land Survey System, so deeds around Woodside reference sections and townships. Each section is nominally a mile square, about 640 acres, with 36 sections to a township, though real sections near Redwood City vary in size. Keep the legal description for land near Woodside when you talk to a surveyor.
Metes and bounds instead
Acreage around Foster City outside a subdivision is often described by metes and bounds or survey description; the deed and any recorded survey describe it instead.
Which office to call
Recorded documents for a parcel near Redwood City sit in the index kept by the County Recorder, usually searchable by name or document number. Zoning, permits and septic questions near Woodside need the planning or permitting office, town or county, depending on location.
The paper trail behind a parcel
The map is an index, not the title: deeds, subdivision plats and easements for land near Foster City are filed with the County Recorder. Long-held tracts around Redwood City can trace back through a long string of deeds, so a title company can sort it out if money is changing hands.
What a plat shows
Easements on the plat near Woodside limit where you can build or fence; read the notes on the sheet.
When a parcel crosses a boundary
San Mateo County touches Alameda County, San Francisco County, Santa Clara County, and Santa Cruz County, and each of those keeps its own parcel map. Acreage along the edge near Foster City can show up in two county records, so check the adjacent map as well. For property near Atherton, the Platbookmapper state page links every bordering county map across California.
Requesting the plat
For a home near Woodside, many recorder offices offer an online index, otherwise call or visit with the reference; small fees are common.
Frequently asked
Are old plats online around Foster City?
In most cases, older plats near San Mateo may be on film or paper.
Do easements show on the plat near Foster City?
For a home near Belmont, dashed lines often mark easements or building lines, so check before you build.
What is a lot and block description around Redwood City?
If you're looking near Atherton, lot and block refer to a numbered lot within a block on a recorded subdivision plat, so pull that plat for dimensions.
What is a replat for land near Belmont?
In most cases, combining or splitting lots near Belmont usually needs a recorded plat change; ask staff about the process.
Where do I find the parcel number for land near Woodside?
It's the number the County Assessor uses to track a tract near Woodside; copy it before you call anyone.
Open the official San Mateo 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.