Prior to 1700, Allegheny County was mostly occupied by wandering tribes of Native American Indians, including the Allegwi, for whom the county is named. In the 1750’s, both the French and the British wanted control of the river communities that developed along the three rivers that meet in what is now Pittsburgh: the Allegheny, the Monongahela and the Ohio. By 1763, at the end of the French and Indian War, British General Edward Braddock had driven the French from Fort Duquesne, which the British renamed Pittsburgh. Over the next decade, white settlers pressured the government to create a separate Allegheny County, with Pittsburgh as the county seat.

The county was officially created on September 24, 1788 from parts of Washington and Westmoreland Counties. The county originally extended all the way to the shores of Lake Erie and became the ‘mother county’ for most of what is now northwestern Pennsylvania. By 1800, the county’s current borders had been set. From the mid-19th to the late 20th centuries, the area was dominated by and prospered from the steel industry. It has now become a center of high tech, and it is home to the Pittsburgh Pirates, the Pittsburgh Penguins, and the Pittsburgh Steelers.