Blog · October 14, 2026 · Pennsylvania
Castle Shannon Plat Map, Pennsylvania: plats and lots
Lots in Castle Shannon trace back to recorded plats filed with the county.
Main page: Allegheny County, PA GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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Trying to understand lot lines near Dormont? What you want is the Castle Shannon plat map, since it shows lots, streets and easements as approved. In this Castle Shannon guide: where to request a copy, plat versus tax map, and the details that matter to buyers.
Getting started with the Castle Shannon plat map
For a subdivision near Whitehall, the deed or parcel record often names the subdivision and plat reference; use it to request a copy.
Where the parcel data lives
Begin with the Allegheny County ArcGIS parcel map; it includes each assessed parcel in the county, Brentwood included. Closer to Bethel Park, enter a street address, an owner's name or a parcel number, and the viewer zooms to the match. For acreage around Mount Oliver, the record panel usually lists the owner of record, acreage on the tax roll, a parcel ID and often a sale date.
Land on the county line
Allegheny County touches Armstrong County, Beaver County, Butler County, Washington County, and Westmoreland County; every one of them runs a separate parcel map. Ground near Whitehall that runs to the line can show up across two assessors' files, so open the adjacent map before you assume the acreage. Out toward Mount Oliver, our state page links each neighboring county map for Pennsylvania.
Castle Shannon, PA: the basics
Castle Shannon sits in Allegheny County, Pennsylvania, so its parcels are on the county's map. If you're looking near Mount Oliver, city or town hall handles matters such as zoning, permits and utilities within town limits, while the county keeps the tax map. Lots just outside the city limits toward Dormont often falls under county rules, not municipal ones.
Reading the legal description
Tracts outside towns near Bethel Park are often described by metes and bounds, which trace the boundary call by call. Subdivision lots in Brentwood usually use lot and block from a recorded plat instead, which is simpler to follow. Write down the legal description for the tract near Mount Oliver for any title or survey request.
Recorded plat or GIS layer
If the tax map and plat differ near Mount Oliver, the recorded plat and a survey control.
Lots, blocks and easements
With a lot near Mount Oliver, the sheet usually includes lot and block numbers, dimensions and bearings, street rights-of-way and easements.
A quick look at the area
Pittsburgh serves as the county seat, home to the main records offices. You'll also find Whitehall, Dormont, Brentwood, and Bethel Park. About 1,224,825 people live in Allegheny County (Census estimate, 2023) across roughly 730 square miles. Allegheny County dates to 1788, and some chains of title near Mount Oliver are long. Landmarks such as Allegheny River and Monongahela River make handy reference points on the map near Brentwood.
A word on accuracy
The acreage figure is an assessed number; only a licensed surveyor sets the real boundary for a parcel near Mount Oliver. For a tract near Green Tree, owner names and values update on a schedule, so a deed recorded last month may not show yet.
Getting a copy
If you're looking near Green Tree, some counties put plat images online, while others require a visit or a request; copy fees are usually small.
Getting answers from the right desk
If the acreage or value on a parcel near Whitehall looks off belong with the county assessment office, since that office keeps the assessment data. Questions about what you can build around Whitehall are for the local planning and health departments, town or county, depending on location.
Amended plats
Lots near Bethel Park can be combined or reconfigured by a replat, search the index for replats of the same subdivision; street vacations near Whitehall show up in the records too.
Using it on a phone
Most viewers work in a phone browser, which helps when you're standing on land near Dormont, so load it before you lose signal. A screenshot of the parcel near Whitehall with its ID keeps working without signal.
Backing up the map with records
The map is an index, not the title: deeds, plats and easements covering ground around Mount Oliver are kept by the Recorder of Deeds. Older tracts near Brentwood can sit on a long string of deeds, so a title company can sort it out if money is changing hands.
Land outside a subdivision
Acreage around Whitehall outside a subdivision may have no plat at all; the deed and any recorded survey describe it instead.
Castle Shannon: common questions
Do easements show on the plat near Whitehall?
With a lot near Bethel Park, dashed lines often mark easements or building lines; read the plat notes.
How do I get a copy of a plat in Castle Shannon?
For a home near Whitehall, copies come from the Recorder of Deeds, often through an online index.
Where are historic plats for Castle Shannon?
For a parcel near Mount Oliver, it varies; some offices have scanned older plats and some haven't.
Is a plat map a survey for land near Brentwood?
It depends, but the plat near Dormont is recorded, while the GIS layer is an approximation.
Is the parcel map a survey around Bethel Park?
No; boundary questions near Green Tree need a licensed surveyor; a survey sets the real corners
Open the official Allegheny County, PA 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.