At the end of the 19th century, downtown Chicago was suffering from endless gridlock. Thousands of horse-drawn wagons crammed the streets daily, delivering endless tons of coal to heat the Loop's soaring skyscrapers and hauling away the resulting mountain of ashes. City leaders were desperate for a solution, but no one wanted to tear up the streets to build a freight subway.
Enter the Illinois Telephone and Telegraph Company. In 1899, they secured a city franchise to dig small conduits under the streets to lay telephone wires. What the city council did not realize was that the developers had much bigger plans.
Digging quietly 40 feet beneath the surface inside Chicago's dense clay layer, crews carved out tunnels that were six feet wide and seven-and-a-half feet high—far larger than necessary for phone lines. To maintain secrecy, workers hauled excavated clay out through hidden building basements and loaded it onto scows along the Chicago River late at night. By the time the city discovered the ruse in 1902, miles of subterranean track had already been laid.
Rather than forcing the company to fill in the subways, the city granted a revised franchise allowing freight transportation. The network eventually grew to over 60 miles of narrow-gauge railway powered by overhead electric lines. Tiny trains zipped beneath the city, delivering coal straight to basement boiler rooms, moving merchandise directly into department store vaults like Marshall Field's, and collecting ash.
At its peak, the Chicago Tunnel Company moved thousands of tons of freight daily without a single truck clogging the streets above. The system eventually succumbed to diesel trucking and oil heat in the 1950s, but the silent labyrinth remained intact—gaining modern fame in 1992 when an offshore pile driver accidentally breached a tunnel wall, pouring 250 million gallons of river water into downtown basements.