River cruises can give you a whole new perspective on the American landscape, as you ply the mighty Mississippi on a steamboat, follow in Lewis and Clark's wake out west, or check out the foliage in New York. The pace is slow and the water is typically calm, making for a relaxed journey. Even more relaxing: Not having to shell out for an international plane ticket, or a plane ticket at all, if you are within driving distance of the embarkation port. Here are some of the top U.S. river cruise itineraries.