Run your hand along the dark brick wall where one era of building reached its limit. The northern half of the Monadnock, finished in 1891 by Burnham and Root, is the tallest commercial building ever raised on load-bearing brick alone, with no steel skeleton inside. To hold up sixteen stories, the walls at street level had to be a full six feet thick, and the whole mass settled so heavily that the ground floor sits below the sidewalk.
Run your hand along the dark, swelling brick and you feel a wall doing the work a steel frame would soon do invisibly. The southern half, built just two years later, used a steel frame and proved the old method obsolete almost overnight. Notice that sheer brown face, undecorated and severe: it holds both the climax and the quiet death of masonry construction in one block.