Contrary to what many believe, the Mississippi is technically not the USA's longest river. That title belongs to the Missouri River, which runs over 3.7k km (over 2.3k mi.) before joining the Mississippi in St. Louis, Missouri. Over its course, towns and cities in ten different states owe their existence to the mighty waterway. In this drone video by North Sky Aerial Imaging, you'll get a bird's eye look at the river as it flows through one of these cities, the South Dakota state capital of Pierre.