The Monadnock Building
The north end of the Monadnock Building was the last tall building built in downtown Chicago with load-bearing wall construction. That's why its lower floors flare out: to be thick enough to carry the 15 floors above. (16 floors is the maximum height that could be built using that sort of construction.)
The south end of the building, with the cornice, was built using iron-frame construction, that was pioneered in Chicago with the Home Insurance Building. The brick and stone is structural on the north end; the brick and stone on the south end is strictly decorative, hiding the structural framework beneath.
The Monadnock Building
The north end of the Monadnock Building was the last tall building built in downtown Chicago with load-bearing wall construction. That's why its lower floors flare out: to be thick enough to carry the 15 floors above. (16 floors is the maximum height that could be built using that sort of construction.)
The south end of the building, with the cornice, was built using iron-frame construction, that was pioneered in Chicago with the Home Insurance Building. The brick and stone is structural on the north end; the brick and stone on the south end is strictly decorative, hiding the structural framework beneath.