One of the most beautiful steam locomotives ever built, the S1 was designed by Raymond Loewe. Poor balancing caused wheel-spin and only one was ever built, for the Pennsylvania Railroad in 1939.
Union Pacific reached out to EMD for more power, and the result was the behemoth EMD DDA40X. Often cited as both the largest and most powerful diesel-electric locomotive ever built, the 98-foot, 5-inch, 475,830-pound machine is staggering. The prime movers are a pair of EMD 16-645E3A diesels.
The King class was also the most powerful ever British 4-6-0 design; it had the highest permissible axle load of 22½ tons, and the largest fire grate of 34.3 square feet of any British narrow firebox locomotive design.
Hydrogen-powered fuel cells, combined with batteries to store electricity, would be a zero-emissions solution to replace the diesel-electric locomotive, Moslener says.
Alco PA LocomotivesArguably the most beautiful diesel locomotive ever built, sadly no Alco PAs were originally preserved. Today, one is under restoration.
Puffing Billy is the world's oldest surviving steam locomotive, constructed in 1813–1814 by colliery viewer William Hedley, enginewright Jonathan Forster and blacksmith Timothy Hackworth for Christopher Blackett, the owner of Wylam Colliery near Newcastle upon Tyne, in the United Kingdom.
The Big Boy has the longest engine body of any reciprocating steam locomotive, longer than two 40-foot buses. They were also the heaviest reciprocating steam locomotives ever built; the combined weight of the 772,250 lb (350,290 kg) engine and 436,500 lb (198,000 kg) tender outweighed a Boeing 747.