Jack Delano was one of the photographers who worked in Roy Stryker’s Farm Security Administration photography program in the early 1940s, traveling the American countryside, photographing people and places with the stated goal of “introducing America to Americans.” In 1942 and ’43, Delano spent time in the rail yards of Chicago, documenting the busy freight hub and the countless workers who kept the trains running 24 hours a day. Some of his most striking images were made on Kodachrome color transparencies, wonderfully preserved in the Library of Congress today. Collected below, a handful of images from Chicago as it was some 75 years ago.