Altoona, Pennsylvania in the context of Horseshoe Curve (Pennsylvania)

Western Pennsylvania is a region in the Commonwealth of Pennsylvania encompassing the western half of the state. Pittsburgh is the region's principal city, with a metropolitan area population of about 2.4 million people, and serves as its economic and cultural center. Erie, Altoona, and Johnstown are its other metropolitan centers. As of the 2020 census, Western Pennsylvania had a population of 3,753,944.

Although the Commonwealth does not designate Western Pennsylvania as an official region of the state, it has retained a distinct identity since the colonial-era Province of Pennsylvania because of its geographical distance from Philadelphia, the state's first settlement, and because of its topographical separation from eastern Pennsylvania, including the Appalachian Mountains, which characterizes the region. The strong cultural identity of Western Pennsylvania is reinforced by the state supreme court, which convenes in Pittsburgh in addition to Harrisburg and Philadelphia.

The Allegheny Mountain Range (/ˌælɪˈɡeɪni/ AL-ih-GAY-nee)—also spelled Alleghany or Allegany, less formally the Alleghenies—is part of the vast Appalachian Mountain Range of the Eastern United States and Canada. Historically, it represented a significant barrier to westward land travel and development. The Alleghenies have a northeast–southwest orientation, running for about 300 miles (480 km) from north-central Pennsylvania southward, through western Maryland and eastern West Virginia.

The Alleghenies comprise the rugged western-central portion of the Appalachians. They rise to 4,862 feet (1,482 m) in northeastern West Virginia. In the east, they are dominated by a high, steep escarpment known as the Allegheny Front. In the west, they slope down into the closely associated Allegheny Plateau, which extends into Ohio and Kentucky. The principal settlements of the Alleghenies are Altoona, State College, and Johnstown, Pennsylvania; and Cumberland, Maryland.

Mount Union is a borough in Huntingdon County, Pennsylvania, United States, approximately 44 miles (71 km) southeast of Altoona and 12 miles (19 km) southeast of Huntingdon, on the Juniata River. In the vicinity are found bituminous coal, ganister rock, fire clay, and some timber. A major Easter grass factory is located in the northern quadrant of the borough limits; until May 2007, the facility was owned by Bleyer Industries. The population was 2,447 at the 2010 census.

The Pennsylvanian is a 444-mile (715 km) daily daytime Amtrak train running between New York City and Pittsburgh via Philadelphia. The trains travel across the Appalachian Mountains, through Pennsylvania's capital Harrisburg, the Pennsylvania Dutch Country, suburban and central Philadelphia, and New Jersey en route to New York. The entire train ride takes about 9 hours total: 1.5 hours between New York and Philadelphia, 2 hours between Philadelphia and Harrisburg, and 5.5 hours between Harrisburg and Pittsburgh.

The Pennsylvanian uses the same Amtrak-owned Philadelphia to Harrisburg Main Line as the Keystone Service trains, but continues further west via the Pittsburgh Line through Altoona and the Allegheny Mountains, eventually terminating its run in Pittsburgh. The Main Line and Pittsburgh Line collectively make up the Keystone Corridor, a federally-designated corridor for high-speed rail service.

The Pittsburgh Line is the Norfolk Southern Railway's primary east–west artery in its Pittsburgh Division and Harrisburg Division across the U.S. state of Pennsylvania and is part of the Keystone Corridor, Amtrak-Norfolk Southern's combined rail corridor.

The Pittsburgh Line spans 248 miles (399 km) between its namesake city of Pittsburgh (PT 353.3) and the state capital in Harrisburg (PT 105.1), crossing the Allegheny Mountains through the Gallitzin Tunnels west of Altoona and the famous Horseshoe Curve in the process. Its east end connects with the railroad's Harrisburg Line HP 112.9) to Reading and Philadelphia, and the west end connects to the Fort Wayne Line to Conway, Pennsylvania, and points west in Ohio and Indiana.