U.S. Marshals Service >> Local District Offices >> Western District of Pennsylvania >> Area of Service 
U.S. Marshals Service offices are based on the organizational structure of the Federal District Court system.  Pennsylvania is divided into three judicial districts that are referred to as the Eastern, Middle, and Western Districts of Pennsylvania.
Map of Pennsylvania, Western District Highlighted

Western District of Pennsylvania:

The Western District comprises the counties of  Allegheny, Armstrong, Beaver, Bedford, Blair, Butler, Cambria, Clarion, Clearfield, Crawford, Elk, Erie, Fayette, Forest, Greene, Indiana, Jefferson, Lawrence, McKean, Mercer, Somerset, Venango, Warren, Washington and Westmoreland.

Court for the Western District is held in Pittsburgh, Erie and Johnstown. 
For Marshals Service office contacts in other counties:
Map of Pennsylvania, Eastern District Highlighted

Eastern District of Pennsylvania:

The Eastern District comprises the counties of Berks, Bucks, Chester, Delaware, Lancaster, Lehigh, Montgomery, Northampton and Philadelphia. 

Court for the Eastern District is held in Philadelphia, Allentown, Easton and Reading. 

Map of Pennsylvania, Middle District Highlighted Middle District of Pennsylvania:

The Middle District of Pennsylvania comprises the counties of  Adams, Bradford, Cameron, Carbon, Centre, Clinton, Columbia, Cumberland, Dauphin, Franklin, Fulton, Huntingdon, Juniata, Lackawanna, Lebanon, Luzerne, Lycoming, Mifflin, Monroe, Montour, Northumberland, Perry, Pike, Potter, Schuylkill, Snyder, Sullivan, Susquehanna, Tioga, Union, Wayne, Wyoming and York. 

Court for the Middle District is held in Scranton, Harrisburg,  Wilkesbarre and Williamsport.
The organizational structure of the district can be found in the United States Code Title 28, Part I, Chapter 5, Section 118.