How did Burnham and Root help solve the challenge of building tall structures on Chicago’s soft soil?

To address the challenge of building tall, heavy structures on Chicago’s unstable, soft clay soil, the architectural firm of Daniel Burnham and John Wellborn Root devised an innovative foundation footing.1

For the Montauk Building (1882–83), which is often cited as one of the first skyscrapers, the firm developed a foundation consisting of a broad slab of concrete reinforced with iron rails. This design effectively distributed the weight of the building, allowing it—and subsequent taller, heavier structures—to remain stable despite the city's soft ground. This engineering solution was a critical development that helped the firm lead the way in the evolution of commercial architecture in Chicago.1