7. Chicago Freight Tunnels, Chicago, Illinois
Location: Illinois’s Chicago
1804 is the year.
Building costs: $30 million*
The Chicago Freight Tunnels were in operation from 1904 to 1959, but nobody knew about them until a massive flood happened a few years later, at which point everyone realized they had existed. The Chicago Tunnel Co. spent five years building these now-vacant tunnels. Mankind was required to manually excavate vast amounts of blue clay soil.
Chicago, Illinois’s Chicago Freight Tunnels ©Stock Montage/Images via Getty
Low-lying waterfront areas were then constructed using the clay. In an extremely risky business move, the Chicago Tunnel Co. constructed sixty miles of tunnels before gaining a single customer. It paid off because customers did show up, and Chicago Tunnel Co. kept digging tunnels and coming up with innovative products (such as natural air conditioning) until the middle of the 1950s.
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