4. The portage included over 36 miles of railway
The challenge faced by the engineers and designers of the Allegheny Portage Railroad included moving railcars up and down a 1,400-foot mountain. The Pennsylvania Legislature passed a law which prohibited any section of the inclines exceeding a 12% gradient. The inclines were limited in their length by the extant technology. Both the power of the reciprocating steam engines and the strength of hemp ropes shortened the desired length of the inclines. They averaged about a half-mile in length. The inclines connected to level grades, where the cars were initially moved by animal power, later replaced with steam locomotives.
The eleven-level grades varied in length. The shortest of the levels reached only .15 miles, the longest stretched over 14 miles. The 12% gradient limit led the engineers to design the inclines so that none exceeded 10%, the steepest incline, number 8, came the closest at 9.9%. Safely pulling the cars required hemp ropes over seven inches in circumference, connected to drive wheels driven by the stationary engines. For additional safety, whenever possible, cars were connected to each other to serve as counterweights, one rising and the other descending, to ease the strain on the engines. The head (top) of each incline featured an engine shed, while at the base a hitching shed stood to protect workers from the elements while connecting the cars.