Man operates uncoupling of the freight cars during the Hump operation at a railroad classification yards in Enola Pennsylvania

Development of the railroad transportation in the United States. Animated map depicts the network of railroads in America. Freight trains parked on railroads at a yard. Buildings in the background. Train moves on railroads. Smoke being emitted from the engine. Trademarks of various railroad companies including Missouri Pacific Lines, Canadian Pacific, Illinois Central and New York Central. Freight cars reach the Hump operation in railroad classification yard at Enola, Pennsylvania. Railroad cars undergo an inspection during their course. Railroad cars are are uncoupled and they move on tracks with gravity. Man operates at control tower. Tower operator works on the teletype list of number of railroad cars. He operates the switches and changes the tracks. View of refrigerator cars, flat cars, coal cars, steel cars, tanker, container and merchandised cars.