5. Part of the subway tunnels were hand-carved
The subway system didn’t come about until the 1930s, and as a result of construction conditions, different methods had to be used, like hand-carving. According to Garfield, “Parts of the underground construction were not so stable, so workers had to hand-dig the tunnel with large knives to exhume out dense clay.” Since the tunnel was also under pressure, workers had to go in and out of pressure chambers throughout construction.
6. The State Street Subway once took a ride down Lake Michigan
The State Street Red Line crosses under the river much closer to the surface than the Blue, so to complete construction, that section of the subway was prefabricated in a South Chicago shipyard then floated up the lake and sunk into the river. You’d think a project like this back in the '30s would suffer from some lack of urban planning and “Oh crap, there’s a wall,” but construction workers came across only mild building settlement and managed to deliver the project on schedule, according to Garfield.