ruling grade

The term "ruling grade" refers to the steepest incline on a railroad line that dictates the maximum weight of a train an engine can pull. This concept was particularly significant in the development of American railroads, where engineers had to contend with challenging terrain.12

Early American railroads, unlike their British counterparts, were designed for strength and durability to navigate varied landscapes and economic conditions. The Baltimore and Ohio Railroad, for instance, faced steep grades in western Maryland. The engineers had to manage a significant incline, which became known as the "ruling grade" because it determined the locomotive power needed for the entire line. This ruling grade, around 2.2 percent, became a standard for many North American railroads.2