The Mississippi, Ohio, Missouri, Illinois, and other rivers knit together the American nation over the course of a century. In an era before widespread highways and railroads, the farms and industries of the Midwest poured their goods downriver to markets around the world. The boomtowns of the century—New Orleans, St. Louis, Cincinnati, and many others—thrived and grew on this waterborne commerce. Waterways were so valuable that the nation began building them. The Erie Canal was one.