What is up 4-12-2?

Up 4-12-2 refers to a type of steam locomotive that was used primarily in the United States during the 1930s. The numbers in the name refer to the locomotive's wheel arrangement: there are four leading wheels, twelve driving wheels, and two trailing wheels.

These locomotives were designed for heavy-duty freight hauling, and were among the largest and most powerful ever built. They could generate over 6,000 horsepower and pull loads upwards of 7,000 tons.

Despite their size and power, however, the Up 4-12-2 was not widely used and was eventually phased out in favor of other locomotive designs. Today, only a few examples of these locomotives remain, most of them in museums.