There was a time when the skyline was dominated by the church spire; in the 20th century, the skyscraper—a cathedral of commerce—has been the city's signature. Its forerunner was the commercial loft building, often an ersatz palazzo made of iron cast to look like stone; Louis Sullivan changed the horizontal focus by adding height.

The distinction between a tall building and a skyscraper was drawn by the Flatiron Building—not just a warehouse with office workers, but a statement about the corporation. The first full-fledged skyscraper was the flamboyantly Gothic Woolworth Building; the Chicago Tribune Tower was next; the title of highest building was held for a short time by the Art Deco Chrysler Building; and then the torch passed to the Empire State Building—a symbolic and a technological breakthrough. The International Style, with its curtain walls of glass and aluminum, has been succeeded by the current trend (seen in Houston's Pennzoil Place and Transco Building and in Pittsburgh's PPG Place), which restores to skyscraper architecture its symbolic level and its historic roots. (58 minutes)