John Deere Headquarters -- Moline, Illinois (1964)

This acclaimed headquarters for the tractor manufacturer pioneered the use of weathering steel, which turned a distinctive, soil-like color (due to iron oxide) if left untreated. Company President William Hewitt was being pressured to move the company to the coast, but resisted, with the caveat that the new building represent the company and its employees. Saarinen delivered with what he called “a steel building that was really a steel building,” a strong, dark structure that was more metal than glass.  Photo 5 of 10 in Design Icon: Architect Eero Saarinen