Chicago's population went from barely a hundred in 1830 to nearly 30,000 in 1850. The city, so close to Lake Michigan and on what was essentially a swamp, was hardly above water level, which caused at least two significant issues for the city:
- The roads were so muddy they were "barely impassible"
- Sewage couldn't properly drain, so disease like cholera spread rapidly (ironically the solution at the time was to instead put waste into the river, which until 1900 flowed into the lake, from which everyone drank)
So over the course of 20 years, the city raised downtown between four and 14 feet. They accomplished this seemingly impossible task by large teams of men simultaneously turning jacks, and then building new foundation below.
Perhaps more amazingly, many old buildings were even lifted and moved for more modernistic buildings to be built in their place.