Even before the attack on Pearl Harbor and the the official entry of the United States into World War II, a massive mobilization effort had begun, carried by the nation’s railroads.

With German submarines disrupting oceanic shipping, more freight was transported by railroad. When rationing on gasoline and rubber was introduced, civilians flocked to train transportation, doubling railroad passenger traffic between 1940 and 1944.

With enlisted men heading overseas, railroad companies turned to women to keep their overtaxed locomotives maintained and running smoothly. By 1945, some 116,000 women were working on railroads.

In April 1943, Office of War Information photographer Jack Delano photographed the women of the Chicago & North Western Railroad roundhouse in Clinton, Iowa, as they kept the hulking engines cleaned, lubricated and ready to support the war effort.