When Frenchmen Charles Blondin became the first daredevil to tightrope walk across Niagara Falls in June 1859, he opened the doors of imagination for all sorts of human ingenuity (and stupidity) for which the Falls became famous for more than a century. Since that day, Niagara Falls has become ingrained in the fabric of America's soul, an icon of its all-natural beauty and, for a long time, its most famous spiritual and tourist hotspot, cherished...