In the decades after the Civil War, cities in the United States grew at an incredible rate. In 1860, only nine cities had a population of more than 100,000. By 1880 that number had more than doubled to 20. Twenty years later in 1900, there were 38 cities with over 100,000 residents. By 1920, with 68 such cities, the country’s urban population exceeded that of rural areas for the first time in American history. New York City led the way with a population of nearly 3,500,000 in 1900, but other cities like Chicago weren’t far behind. Over a 40 year period, Chicago’s population grew from 100,000 to 1,700,000. This massive growth was driven by three factors: immigration, migration and industrialization