Horseshoe Curve (Pennsylvania)

Horseshoe Curve is a three-track railroad curve on the Norfolk Southern Railway's Pittsburgh Line in Blair County, Pennsylvania. The curve itself is about long and in diameter; it was completed in 1854 by the Pennsylvania Railroad as a way to lessen the grade to the summit of the Allegheny Mountains. It eventually replaced the time-consuming Allegheny Portage Railroad, the only other route across the mountains for large vehicles.