This contemporary drawing shows one of the inclined planes with its engine house at the top of the hill.

The National Park Service has a visitor center and reconstructed engine house at the summit of the works, west of Hollidaysburg. The APRR operated from 1834 to 1854 when the Pennsylvania Railroad arrived.

For more on the APRR, see this superb 20-minute video from the Park Service.
Also see:
- The National Park Service site.
- Here, and
- Here.
- This is the best historical map (scroll down).

All fine, but Jay and I were interested in the terrain. Why did they build it where they did?