Have you ever wondered why the eastern half of the United States is densely populated, while everything west of Omaha is no man’s land? Most people would assume that it’s because people first settled in the east and moved West, or perhaps they believe it’s because of the vast desert that takes up most of the southwest. It’s actually more complicated than that. Topography and rainfall have created what appears to be a straight line down the middle of the country that dictates population density, and 80% of Americans live east of the line, while only 20% live to the west. Several large cities border the American frontier — San Antonio, Austin, Fort Worth, Oklahoma City, Wichita, Omaha, Lincoln, Sioux Falls and Fargo. There isn't much west of those cities until you reach western California and the Pacific Northwest. It turns out that the major reason why the population changes drastically is rainfall. It rains much more on the east side of the line versus the west. The reason for the drastic change in rainfall is that the Rocky Mountains create a colossal wall known as a rain shadow that prevents moisture from passing from the Pacific Ocean. This has created a large swath of dry land that’s not conducive to larger populations. Who would have thought that something as simple as rainfall could divide the nation in such a way?
