World War I
Heavy wartime traffic exposed coordination problems among private railroads. The federal government temporarily operated the railroads through the United States Railroad Administration during and immediately after the war.
World War II
Railroads carried enormous wartime traffic while gasoline and rubber were rationed. Passenger trains moved service members while freight trains supplied factories, ports, bases, and military operations.
Doing more with the system
The industry handled extraordinary demand through intensive use of locomotives, cars, track, terminals, and employees.
After the wars
Wartime traffic demonstrated rail capacity, but postwar growth of automobiles, airlines, highways, and trucking soon changed the transportation market.