As shown on the History Channel. Between 1880 and 1930, nearly 24 million new immigrants arrive in America. Many go to work building a new frontier: the modern city, one of America's greatest inventions. The high cost of land in cities like New York and Chicago means the only way to build is up. A new kind of building, the skyscraper, is made possible by steel. Produced on a massive scale by Scottish immigrant Andrew Carnegie, steel production underpins the infrastructure of the modern city. This new urban frontier draws rural migrants and newly arrived immigrant workers. For many, the Statue of Liberty is their first sight of the New World and Ellis Island is the gateway to the American Dream. The lawless city offers opportunities for many, astronomical wealth for a few. In New York, police chief Thomas Byrnes uses his violent new innovation "the third degree" to keep a lid on crime. The millions flocking to urban areas often experience terrible conditions in disease-ridden tenements. Jacob Riis, photographer and reformer, brings their plight to the world with his groundbreaking photographs in the book "How the Other Half Lives." Workers in new high-rise factories become urban martyrs in New York City's Triangle Shirtwaist factory fire, as the city struggles to make these new buildings safe. Powered by steel and electricity, the city begins to be tamed and defined by mass transportation, stunning skylines, electric light...and the innovative, industrious American spirit.