Chicago's Great Elevation: Streets Lifted by Thousands of Screws Beneath Occupied Shops
Facing a Lake Michigan–flat terrain that blocked drainage, Chicago in the 1850s–60s raised entire blocks and buildings by threading heavy jackscrews beneath them, including a 320‑foot block lifted four feet eight inches on about 6,000 screws with synchronized turns while shops stayed open. The move followed a plan to place sewers at street level under fill, creating gravity drainage despite minimal slope, a controversial but politically palatable compromise. The technique required exposing foundations, using needles through walls, and lifting evenly to avoid damage, sparking a brief boom in such work and completing key lifts like Randolph & Dearborn and Tremont House, with George Pullman later involved; lifting largely declined by the mid‑1860s.