John F. Sears, author of "Sacred Places: American Tourist Attractions in the Nineteenth Century." Sears went back to magazines, fiction and painting of the 19th century to find out when and why tourism developed in this country. He says that natural wonders like Niagara Falls and Yellowstone were a substitute for the cathedrals of Europe, and that tourism gave Americans a way to shape their national identity. (Interview by Sedge Thomson)