In the United States, sand domes grew to mammoth proportions in order to allow locomotives to travel extended distances. The Union Pacific "Big Boys," the 4000-series locomotives of the 1940s, had 10-foot wide by 14-foot long domes holding nearly 1,500 pounds of sand. Even in the iciest dead of winter, they ranged from North Platte, Neb. to Ogden, Utah., more than 500 miles, without refreshing their sand supplies.