Blog · October 14, 2026 · Pennsylvania
Reading the Dormont Plat Map for a lot
Lots in Dormont 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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If a legal description for land in Dormont cites a lot number, look up the Dormont plat map it refers to. This Dormont guide covers: where plats are filed, how a plat differs from a parcel map, and what to look for on the sheet.
Who keeps the Dormont plat map
For a lot near McKeesport, the deed or parcel record often names the subdivision and plat reference; use it to request a copy.
The viewer Allegheny County publishes
Your first stop is the Allegheny County ArcGIS parcel map; it maps each tax parcel around Crafton and Castle Shannon. Closer to Mount Oliver, enter a street address, an owner's name or a parcel number, then pick the result to center the map on it. For property near Heidelberg, a pop-up or side panel usually lists the owner of record, assessed acreage, a parcel ID and sometimes recent sales.
When a plat changes
Lots near Heidelberg can be combined or reconfigured by a replat, so check for later filings; street vacations near Carnegie show up in the records too.
What the map can't tell you
Acreage on the record is an assessed number; only a licensed surveyor sets the real corners for a parcel near Crafton. Closer to Mount Oliver, owner names and values update on a schedule, so a deed recorded last month might lag behind.
Recorded documents worth pulling
The map is an index, not the title: deeds, subdivision plats and easements for land near Castle Shannon are filed with the Recorder of Deeds. If the land is near Green Tree, have ready the document number shown in the record panel so staff can find the deed fast.
Where Dormont fits in
The town lies within Allegheny County, Pennsylvania, so its parcels are on the county's map for land near Pittsburgh. For a parcel near Carnegie, city or town hall handles things like zoning, permits and utilities within town limits, while the county keeps the tax map. Lots just outside the city limits toward Heidelberg often follows county rules, not municipal ones.
Two different maps
Where lines don't match in Dormont, trust the recorded documents over the GIS layer.
Land on the county line
Allegheny County borders Armstrong County, Beaver County, Butler County, Washington County, and Westmoreland County, all with their own assessor records. Ground near Castle Shannon that runs to the line can be split across two assessors' files, so check the adjacent map before you assume the acreage. If the land is near Carnegie, our state page links every bordering county map across Pennsylvania.
Reading the legal description
Tracts outside towns near Carnegie are often described by metes and bounds, a series of courses and distances from a starting point. Platted lots around Heidelberg are typically described by lot and block, making them easier to find. Keep the legal description for land near Crafton when you talk to a surveyor.
Field tips
The parcel map usually runs in a mobile browser, handy when you're parked on a road near Castle Shannon, but coverage can be spotty out of town. A printout of the tract near Mount Oliver is a good backup.
Getting your bearings
Pittsburgh serves as the county seat, home to the main records offices. Other places on the map include Green Tree, Castle Shannon, Carnegie, and Heidelberg, each with its own cluster of lots. Roughly 1,224,825 people call Allegheny County home (Census estimate, 2023) on roughly 730 square miles. Allegheny County dates to 1788, which matters when you trace an old farm's title. Landmarks such as Allegheny River and Monongahela River help you orient on the aerial around Carnegie.
Metes and bounds instead
Acreage around Castle Shannon outside a subdivision is often described by metes and bounds or survey description; look for a recorded survey for land near Heidelberg.
Getting answers from the right desk
If the acreage or value on a parcel near Mount Oliver looks off go to the county assessment office, since that office keeps the assessment data. Zoning, permits and septic questions near Carnegie go to planning, building or health offices, town or county, depending on location.
Reading the plat sheet
Utility or drainage strips on a lot in Dormont limit where you can build or fence; check the plat notes and any covenants.
Getting a copy
If you're looking near Mount Oliver, many recorder offices offer an online index, otherwise call or visit with the reference; copy fees are usually small.
Questions about the Dormont plat map
Where can I find the Dormont plat map?
Good question; recorded plats near Green Tree are filed with the Recorder of Deeds; use the plat reference from the deed or parcel record.
Are old plats online near Heidelberg?
For acreage around Green Tree, it varies; some offices have scanned older plats and some haven't.
Is a plat map a survey near Crafton?
For most people, the plat near Mount Oliver is recorded, while the GIS layer is an approximation.
What is a replat in Dormont?
Short answer: lot splits in Dormont go through the planning office; ask staff about the process.
Does the parcel map work on a phone near Crafton?
For a parcel near Heidelberg, most viewers run in a mobile browser; screenshots help offline.
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.