In 1956, the visionary architect Frank Lloyd Wright sketched out plans for The Illinois, a mile-high skyscraper that would accommodate 100,000 people, parking for 15,000 cars and enough office space to house the entire state government. Sheathed in aluminum and stainless steel, Wright's 528-story edifice could have been built, he believed, with available technology. But a significant barrier stood in the way: the required elevators would have taken up too much space.