In the late 1930s and early 1940s, the American steam passenger locomotive reached its zenith in a stable of 4-8-4 Northerns that served across the nation. The Union Pacific FEF-3, Norfolk and Western J, Southern Pacific GS-4 and others of their ilk represented the ultimate development of the steam engine, with a combination of power, speed, endurance and mechanical beauty that would not be seen again. And many observers would agree that the last to be built, the New York Central Niagara, was likely the best. To speed passengers over the NYC's 4-track, 928-mile raceway between New York and Chicago, the NYC's Chief Mechanical Engineer, Paul Kiefer, specified an engine with 6000 cylinder horsepower (5000 drawbar horsepower) and near-constant availability - a significant improvement on the Hudsons and Mohawks then reigning on the Water Level Route. World War II production restrictions dictated that the new engine be dual service, although it ultimately would be most remembered as a fast passenger locomotive. Like the NYC's other signature engines, it would take its name from a river and have a characteristic long, low look - the result of having to fit within the NYC's maximum height of 15'2", a full foot shorter than the loading gauge of most American railroads.
The designers at American Locomotive Company (Alco) in Schenectady, NY would fit the largest possible boiler into that loading gauge, so large that the sand dome had to be recessed into the boiler top and the smoke stack was a mere stub - hence the use of smoke lifters, or "elephant ears," on either side of the smokebox, which only added to the engine's handsomeness. The steam dome was eliminated by the use of a perforated pipe instead. In many other respects, the Niagara was a direct descendant of the Union Pacific FEF-3s that Alco had recently completed, including its smooth boiler with few added appliances - uncommon in the U.S. but the norm in British design - and its massive 14-wheel centipede tender. To make it possible to fly from new York to Chicago with only one coal stop, the Niagara's tender had an extra-large coal bunker; the resultant smaller water tank was no problem, as the engine could scoop water from pans between the rails at 80 mph.
Delivered in 1945-46, the Niagara fleet was miniscule in comparison to the Central's hundreds of Hudsons and Mohawks - just 27 locomotives, including the class S-1a prototype, 25 class S-1b production engines, and an experimental class S-2a with poppet cylinder valves replacing the normal Baker valve gear. Yet the Niagaras were the premier power for 12 trains daily each way between Grand Central Station and the Windy City, from the 20th Century Limited to the Commodore Vanderbilt and the Chicagoan. The Niagaras' six-days-per-week running schedule, averaging 26,000 miles per month, demanded that maintenance be performed with the precision of a grand prix pit crew. One result was the use of gangs of "hot men" in asbestos suits to enter the firebox with the fire dropped but the engine still in steam, clean tubes and flues, make minor repairs to the brick arches and grates, and return the engine to service.
In a 1946 road trial and cost comparison against the Central's EMD E7's, the Niagara's abilities proved close enough to the new diesels to make EMD's sales reps squirm. Nonetheless, the die had been cast and all Niagaras were retired by July 1956, with none lasting into preservation.