Mather Tower, 75 E. Wacker. Herbert Hugh Riddle, 1928. View from north. (Photograph by Thomas Leslie)
No tower had been built to such slender proportions, and there were few opportunities for diagonal bracing in the tower’s narrow direction because of its river views. . . .
The Mather was so slender that its foundations had to be designed for uplift, and were literally screwed into bedrock.
Taken from Chicago Skyscrapers, 1871-1934 (University of Illinois Press, June 2013).