How steam power worked
Coal, oil, or wood heated water in a boiler. Expanding steam drove pistons connected to the driving wheels.
Why locomotives grew larger
As trains became heavier, railroads developed larger boilers, more driving wheels, and articulated designs to increase power and tractive effort.
Steam's strengths and limits
Steam locomotives could produce enormous pulling power, but they required intensive maintenance, large crews, water, fuel, and servicing facilities.
The end of regular steam
By the 1950s, diesel-electric locomotives had replaced steam on most major U.S. railroads because they were easier to maintain and operate.
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