Others have tried but Nik Wallenda has become the first person ever to cross Niagara Falls on a high wire. The daredevil successfully negotiated walking a two-inch-wide wire strung through heavy mist some 200 feet above the roaring waters of Horseshoe Falls. Wallenda said the stunt was a tribute to his hero and great-grandfather, Karl Wallenda, who died during a tightrope walk in Puerto Rico in 1978. Next up for Wallenda is a high-wire walk across the Grand Canyon. Video story at ABC News.