Eventually, every railroad faces the same problem: how to move trains over mountains? Small logging and mining railroads purchased geared locomotives - Heislers, Climaxes and Shays - which could pull trains at low speed up steep hills. Medium railroads, like the Delaware, Lackawanna & Western, bought many medium-sized engines - 4-6-2s, 4-8-2s and 4-8-4s - and put as many as ten engines on one train. Large railroads like the Union Pacific Railroad, stretching from Kansas City, Missouri and Omaha, Nebraska to Seattle, Washington and Los Angeles, California, preferred a different solution. The Union Pacific ordered larger, more powerful engines such as the 4-12-2 Union Pacific-type and 4-6-6-4 Challengers. The trend toward size and power culminated in the 1.2 million pound, 6,200 horsepower 4-8-8-4 'Big Boy.'