“In 1840, when the Illinois and Michigan Canal opened connecting the Mississippi River with the Great Lakes, Chicago had a population of four thousand. In 1871, Mrs. O’Leary’s cow burned down a third, perhaps, of the city. Chicago built the world’s first steel-framed skyscraper in 1885, the city had a population of two million by 1900, and at that point 70 percent of its citizens had been born outside the United States.”