Pennsylvania County Research Guide

Allegheny County, Pennsylvania

Formed September 24, 1788 from parts of Washington and Westmoreland Counties — county seat Pittsburgh. Who settled here, why families moved on, and where to look for their records.

Who settled here

By 1790 Pittsburgh was already known as the gateway to the West. Many settlers reached the Ohio country by way of Forbes' Road or Braddock's Road, both of which led to Pittsburgh. Families bought or built flatboats there, loaded their belongings and livestock, and floated downriver on a one-way trip. At the destination the boats were taken apart and the lumber used for shelter.

One account describes the spring rise of 1788 as the peak of the great immigration, when at least 308 flatboats carrying more than 6,000 people, about 3,000 head of livestock, and 150 wagons passed down the Ohio. In dry seasons the river was often too low between Pittsburgh and Wheeling, and Wheeling became the main departure point.

Why families moved on

Records that say exactly why a family left are rare. Treat these as leads, and look for evidence about your own ancestors in deeds, tax lists, court cases, and church records.

Clues to look for

Historical and genealogical societies

Call or write before you visit. Many are volunteer-run with limited hours.

Before Allegheny County existed

Allegheny County was formed in 1788 from parts of Washington and Westmoreland Counties. For records made before then, search the parent counties:

Pennsylvania births, deaths, and state records

Printable Record Checklist

Fill in what you're looking for, print it, and take it with you to the courthouse or library.

Brick Walls & Buckeyes emblem Brick Walls & Buckeyes brickwallsbuckeyes.com · Allegheny County, Pennsylvania

Vital & Estates

Birth record (county register 1893–1905, state certificate 1906+)
Death record (county register 1893–1905, state certificate 1906+)
Marriage license (Register of Wills / Clerk of Orphans' Court)
Will / estate administration file
Orphans' Court or guardianship record
Divorce or civil case (Prothonotary)

Land & Property

Deed / land transfer (Recorder of Deeds)
Mortgage record
Tax assessment list
Original warrant or survey (Pennsylvania State Archives)

Community & Print

Newspaper mention
Historical society family file
Cemetery record / headstone photo
Church record
Census record

Compiled from county and society websites in October 2026. Offices move and details change, so confirm hours and fees before you visit.

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