In March 1831, the Pennsylvania legislature authorized a system in which canal boat passengers and goods would be moved to railroad cars and towed by stationary steam engines up a huge staircase of five inclined planes. On descent, they would be let down five more planes, then transferred again to canal boats.

The portage railroad was a daring stroke of engineering that worked remarkably well during a time when railroads were still experimental. As locomotives grew more powerful and dependable, railroads provided stiffer competition for canals. The portage railroad was abandoned afer 23 years of service when the Pennsylvania Railroad bought the Main Line canal system in 1857.

In 1839, the Commonwealth commissioned Col. Charles L. Schlatter, an engineer, to survey a direct route without inclined planes. He produced three plans-a northern, a southern, and a 'middle route, but the State took no action on his proposals. However, when J. Edgar Thompson was appointed chief engineer of the PRR in 1847, he re-surveyed and improved the middle route, following the valley of the Juniata River.

This provided a good, level route all the way to the foot of the Alleghenies, to what is now Altoona. The next goal was to find a route across the mountains that would not exceed a grade of 1.8% (a rise of 1.8 feet in 100 feet of distance). They crossed some low ridges southwest of Altoona, then came to a valley that ran westward. They followed the ridge that paralleled this valley, and found they could lay rails there with 1.75% grade. But 5½ miles from Altoona they encountered trouble. The valley ran abruptly into a mountain side and split into two deep ravines.

On the other side of the valley, they saw another mountain ridge which they later found would carry their rails at a satisfactory 1.73% grade. It ran southward for a short distance and then westward again up the mountainside to a spot near Gallitizin, where they had determined to tunnel.

However, the question remained on how to get the tracks the other side. To go directly across the valley would have meant building a bridge with a 4.37% grade, too steep for practical rail operations. It was decided to route the tracks directly westward to the first ravine (Kittanning Run) and build a huge fill to take the tracks across it. Then they would slice off the face of the mountain so the tracks would make a big semi-circle. Then, they would go across the second ravine (Burgoon's Run) via another fill in order to reach the ridge on the other side of the valley. The big semi-circle became known as the Horseshoe Curve.

On February 15, 1854, a single track was laid from Altoona to "Summit" and operations began. Over time, it grew to 2 to 3 to 4 (and now back to 3) tracks. It is now part of Norfolk Southern's Pittsburgh Division