No big buildings went up in the Loop for about 20 years, between the Great Depression and the early 1950s, when Chicago's next wave of architectural supremacy crested. Its guiding spirit was Ludwig Mies van der Rohe, who came to Chicago from Berlin in 1938 after the Bauhaus closed. Declaring his affinity for Chicago's earlier tradition, Mies asserted, pace Sullivan, that form is function. Since the steel frame held the building up, there was no need for bricks and stones at all. Among Mies' influential Chicago buildings were the residential towers at 860 and 880 N. Lake Shore Drive, completed in 1951.

The new office skyscrapers that rose downtown between the 1950s and the 1970s were either by Mies or influenced by Mies. For example, Skidmore, Owings & Merrill designed the Inland Steel Building (1954). This is one of my favorite modern buildings. The thin stainless steel and green glass gives it a hammered, almost hand-made look.

Mies himself designed the Federal Center, constructed over the period 1959-74. The conventional view is that these glass boxes are absolutely minimal. Samuelson sees them differently. He points up at the I-beams on the skin. Though these girders serve a function as "stiffeners," they aren't a structural necessity.

Thus Samuelson argues that they constitute a "romantic" and "poetic" element in the tradition of Sullivan--the point being to give the building upward thrust.

Mies inspired Chicago's two giants, the 100-story Hancock Tower (1969) by Skidmore, Owings & Merrill, and the 110-story Sears Tower (1969-74), also by SOM, which was the tallest building in the world when completed.

Chicago loves having the biggest of anything. Unfortunately, the Sears Tower lost its title in 1996, when a skyscraper by Cesar Pelli in Kuala Lumpur, Malaysia, bested it by 22 feet.