"White water! White water!" yelps Neil Kaminsky, an Albuquerque physician and veteran rafter, as he maneuvers through 5 ft.-tall, "haystack" waves on Idaho's roaring Salmon River. It may not be everyone's idea of a great vacation, but Kaminsky counts himself lucky to be out there risking his life. The U.S. Forest Service, which administers the Salmon and other prime Idaho rivers, grants just 1,100 permits to rafting parties annually. They are chosen by lottery from more than 11,000 applicants.
For Americans, heading into the wilderness is more than a national rite -- it is a national right. Until recently, national-park visitors,...