Blog · October 14, 2026 · Pennsylvania
Allegheny County Plat Book: finding and using one
On ground around Carnot-Moon, plat books show ownership by township; the parcel viewer shows it today.
Main page: Allegheny County, PA GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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Want a copy of the Allegheny County plat book? It's a printed atlas of landownership, usually by township, and it's handy for land around Baldwin. This county guide covers: how the atlas is organized, where to look for printed copies, and the free online map that stays current, especially near Allison Park.
The Allegheny County plat book: start here
Closer to Boston, a plat book is a privately published atlas, showing rural owners and tract lines, often organized by township.
The free map to start with
Property in and around Ohio River appear on the Allegheny County ArcGIS parcel map, free to use and open without a login. Without an address in hand, follow Interstate 376 on the aerial and click the parcel itself. In and around Carnot-Moon, copy the parcel ID while you have it open; every office in the county uses it to find the file.
Who uses plat books
Farmers, hunters and appraisers near Duquesne use plat books to see ownership across many tracts at once.
Where to look for one
Editions come and go depending on publishers, try the county extension office, recorder's office or library near Duquesne.
Places you'll see on the map
Pittsburgh serves as the county seat, home to the main records offices. Smaller places on the map include Clairton, Duquesne, McKeesport, and Aspinwall, where town lots give way to larger tracts. About 1,224,825 people call Allegheny County home (Census Bureau estimate, 2023) across roughly 730 square miles. The county was formed in 1788, so old deeds can run back a long way around Carnot-Moon. Features like Allegheny River and Monongahela River are easy to spot when you zoom out.
Limits of the parcel data
For a tract near Allegheny River, the acreage figure is an assessed number; only a licensed surveyor establishes the real lines on the ground. Near Aspinwall, records update in batches, so a deed recorded last month might lag behind.
Offices that can help
If the acreage or value on a parcel near Ohio River looks off go to the county assessment office, since that office keeps the assessment data. Questions about what you can build around Carnot-Moon need the planning or permitting office, and the answer depends on jurisdiction.
Taking the map into the field
Most viewers work in a phone browser, useful out on a road near Carnot-Moon, but coverage can be spotty out of town. A printout of the tract near Allegheny River is a good backup.
The paper trail behind a parcel
When the details count, request the recorded deed through the Recorder of Deeds; the parcel map near Ohio River only summarizes it. For a parcel near Bakerstown, have ready the book and page listed on the parcel record so staff can find the deed fast.
Legal descriptions in Pennsylvania
Older tracts around Duquesne are often described by metes and bounds, a series of courses and distances from a starting point. Platted lots around Boston refer to a recorded plat, making them easier to find. Write down the legal description for the tract near Clairton before you request a deed or survey.
Using the parcel viewer instead
The Allegheny County ArcGIS parcel map is updated more often than any atlas, for tracts near Avalon.
A homemade atlas
Screenshot each section of the viewer around Bairdford and keep them in a binder for the truck.
Atlas or legal document
For land near Baldwin, a plat book is not a recorded plat: the recorded plat at the Recorder of Deeds is a legal document, while the atlas is a reference.
Land on the county line
Allegheny County touches Armstrong County, Beaver County, Butler County, Washington County, and Westmoreland County, and each of those keeps its own parcel map. Ground near Allison Park that runs to the line can be split in two county records, so check the neighboring map too. Near Boston, our state page links every neighboring county map for Pennsylvania.
Quick answers
Is there a current Allegheny County plat book?
Closer to Carnot-Moon, it depends on whether a publisher has a current edition; ask local offices.
Are old plat books online in Allegheny County?
For a tract near Bakerstown, libraries and historical societies hold older editions.
Plat book or parcel viewer near Boston?
Generally, the viewer covers town lots near Ohio River too; many people use both.
How accurate are plat book acreages near Baldwin?
If you're looking near Carnot-Moon, plat book acreage and lines are approximate.
What is a parcel ID near Baldwin?
It's the number the county assessment office uses to track a tract near Allison Park; copy it before you call anyone.
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.