Allegheny County

Regions of Allegheny County

---

The Layers of Allegheny County

Allegheny’s complexity is best understood through its layers of governance and administration. These overlapping jurisdictions shape everyday life, from taxation to policing to education.

Federal Layer – State Layer – County Layer – Municipal Layer – Special Districts and Authorities

---

How to connect all the data

Allegheny DZ DB

---

Origin of Allegheny County

Allegheny County was officially created on September 24, 1788, from portions of Washington and Westmoreland counties. Its establishment was part of Pennsylvania’s broader effort to organize its rapidly growing western frontier in the late 18th century.

Name and Etymology

The name “Allegheny” comes from the Allegheny River, which runs through the northern part of the county and converges with the Monongahela River at Pittsburgh to form the Ohio River. The word itself is believed to be of Lenape (Delaware) origin, interpreted as “beautiful stream.” Early European settlers and cartographers adopted the term, giving it permanence in both river and county names.

Indigenous Presence

Before European colonization, the region was home to Native American peoples, including the Lenape and Shawnee. The strategic meeting of rivers made the area a crossroads for travel, trade, and conflict long before Europeans arrived. Control of the Forks of the Ohio (present-day Pittsburgh) was especially contested during the French and Indian War in the mid-1700s, when both French and British powers sought dominance over the region.

Colonial and Early American Period

• In the 1750s, the French constructed Fort Duquesne at the confluence of the Allegheny and Monongahela rivers.
• The British later captured the site in 1758 and built Fort Pitt, laying the groundwork for Pittsburgh’s founding.
• Following the American Revolution, the new United States encouraged settlement in the Ohio River Valley, spurring migration into western Pennsylvania.

The county’s location—bridging eastern seaboard trade with western territories—made it an early focal point of transportation, industry, and settlement.

Industrial Emergence

By the early 1800s, Pittsburgh and its surroundings became known for glass, iron, and eventually steel production. The rivers provided transportation for goods and raw materials, while local coal deposits fueled industrial growth. This industrial foundation transformed Allegheny County into a national economic hub throughout the 19th and 20th centuries.

Political Development

At its creation, Allegheny County established Pittsburgh as the county seat, cementing the city’s role as the administrative and cultural center. Over time, the county’s governance expanded alongside its population, eventually growing to encompass 130 municipalities, each with its own role within the larger county structure.

Stuff to be Integrated

Flood Special Pennsylvania 1936 by WPA

Pittsburgh flood of 1936

Sanborn Fire Insurance Map