After the Revolutionary War, American families migrated on the Ohio and Mississippi Rivers, typically a one-way trip. When steamboats debuted in 1812 and flatbottom riverboats in 1815, river routes became increasingly accessible.
But American settlement was still primarily confined to the eastern seaboard. The natural barrier of the Appalachian ridge from Canada to Georgia discouraged westward expansion. There was, however, a hole to the west through New York’s Mohawk River Valley. That provided the opportunity to build the Erie Canal, completed in 1825. Hundreds of thousands of immigrants—mostly German and Irish—and 10,000 to 20,000 New Englanders per year traveled the canal to fertile farmland rich with timber and minerals in northern Ohio, southern Michigan, northern Illinois, southern Wisconsin, northern Iowa and Minnesota.
The Pennsylvania Canal, built in 1833, spanned the distance between Philadelphia and Pittsburgh. Along with the Erie Canal, it was an important migration route for just a short time before the railroads took over. Another mostly water route even brought some 40,000 gold enthusiasts to California—across the Isthmus of Panama.