In 1937 Pennsylvania Railroad decided to build a new passenger locomotive to replace its venerable K4 4-6-2s, designed in 1914. The company produced the S1, a spectacular 6-4-4-6 and the largest rigid frame passenger locomotive ever built. They hoped the S1 could haul 1,000 tons at an ambitious 100 miles per hour, but it's length limited its use and its axle loading was undesirably high. Loewy's 1978 lithograph shown at top right was based upon the 1937 drawing shown at bottom right. The S1 looked fast even when it was sitting still. The one-of-a-kind experimental model was exhibited at the 1939 World's Fair in New York City, where it was displayed in operation on rollers. The 1933 Chicago World's Fair and the 1939 New York World's Fair both emphasized the "World of Tomorrow" that would define industrial design for much of the 20th century.