If you are 55 or older, there is hardly a better option for American heritage tours than Elderhostel.(www.elderhostel.com). There are more than 200 trips with a historical focus,from exploring the Oregon Trail to viewing Anasazi rock art in the great canyon areas of Four Corners. Lewis & Clark enthusiasts, there are more than 25 trips focusing on the intrepid exployers, including a kayaking trip to Skamakawa. Elderhostel does an excellent job describing the accommodations and physical requirements of trips.