In Lake Itaska, Minnesota, and flowing S. for 2800 m., enters the Gulf of Mexico by a large delta; its earlier course is through picturesque country, often in gorges, with rapids such as the St. Anthony Falls, the Des Moines and Rock Island Rapids. After receiving the Missouri, 3000 m. long, from the Rocky Mountains, it flows 2½ m. per hour through great alluvial plains, which are protected from its overflows by hundreds of miles of earth embankments, and is joined by the Ohio from the E., the Red and Arkansas Rivers from the W., and many other navigable streams. The Mississippi is navigable by large steamers for 2000 m.; St. Louis, Memphis, Vicksburg, Natchez, and New Orleans are among the chief ports on its banks.