Formed September 24, 1788 (19th county)
Allegheny County (1,250,585), Pittsburgh (302,958)
A brown stone facility is the 1888 Richardsonian Romanesque courthouse in Pittsburgh. The courthouse is on Grant Street between 4th and Forbes avenues. Henry Hobson Richardson is the building designer. United States Highway 30 is four blocks south of the location. There is a 1917 Administrative Building that supports the courthouse. The county was created on September 24, 1788 from parts of Washington and Westmoreland counties as the 19th county with Pittsburgh as the only county seat. Allegheny County is named for the Allegheny River. The county seat is named for British Secretary of State William Pitt the Elder. Allegheny County is the birthplace of 4 Pennsylvania governors, James H. Duff, David L. Lawrence, Richard L. Thornburgh, and Thomas J. Ridge.
Allegheny County government consists of a treasurer, a sheriff, an attorney, a coroner, and a clerk (executive). It has 13 Council Members (legislative.) Fifty-four Common Pleas Court Judges and Forty-six Magistrate Court Judges serve Allegheny County (judicial.) The county is in western Pennsylvania. The Ohio River forms in the county and flows northwest. Erie, Pennsylvania is north and Harrisburg, Pennsylvania is east of the county. The county center is in Pittsburgh 1 mile Northwest of the city center. The county is surrounded clockwise by Butler, Westmoreland, Washington, and Beaver counties.
The area of the county is 745 square miles. It is 30 out of 67 in the state. It ranks 2 out of 67 in population in the state. It has a density of 1678.6 persons per square mile making it 4 out of 67 in the state. Allegheny County has 61.2% of its population in its incorporated areas. Interstate Highway 76 travels through the county from northwest to southeast from Butler County to Westmoreland County. Interstate Highway 79 goes north to south from Butler County to Washington County. United States Highway 19 parallels Interstate Highway 79 from Butler to Washington counties. United States Highway 22 enters from Westmoreland County, east, and exits to Washington County, west. United States Highway 30 comes from Westmoreland County and goes east to Beaver County. The county looks like the head of a hatchet. Pittsburgh dominates the center of the county. Pittsburgh is the county seat and the largest city. It is 24.2% of the county population. The county is pronounced AL-LE-GAE-NEE. This county is in the Pittsburgh Metropolitan Statistical Area.
Aspinwall
Avalon
Baldwin
Bell Acres
Bellevue
Ben Avon
Ben Avon Heights
Bethel Park
Blawnox
Brackenridge
Braddock
Braddock Hills
Bradfordwoods
Brentwood
Bridgeville
Carnegie
Castle Shannon
Chalfant
Cheswick
Churchill
Clairton
Coraopolis
Crafton
Dormont
Dravosburg
Duquesne
East McKeesport
East Pittsburgh
Edgewood
Edgeworth
Elizabeth
Emsworth
Etna
Forest Hills
Fox Chapel
Franklin Park
Glassport
Glenfield
Glen Osborne
Green Tree
Haysville
Heidelberg
Homestead
Ingram
Jefferson Hills
Leetsdale
Liberty
Lincoln
McKeesport
McKees Rocks
Millvale
Mount Oliver
Munhall
Monroeville
North Braddock
Oakdale
Oakmont
Pennsbury Village
Pitcairn
Pittsburgh
Pleasant Hills
Plum
Port Vue
Rankin
Rosslyn Farms
Sewickley
Sewickley Heights
Sewickley Hills
Sharpsburg
Springdale
Swissvale
Tarentum
Thornburg
Turtle Creek
Verona
Versailles
Wall
West Elizabeth
West Homestead
West Mifflin
West View
Whitaker
Whitehall
White Oak
Wilkinsburg
Wilmerding
McDonald
Trafford