The Pan-American Exposition in Buffalo, New York, dazzled with its new rainbow-colored electric lights. It showcased an array of wonders, like daredevils attempting to go over Niagara Falls in a barrel, or the "Animal King" putting the smallest woman in the world and also terrifying animals on display. But the thrill-seeking spectators little suspected that an assassin walked the fairgrounds, waiting for President William McKinley to arrive. In...