President Trump has repeatedly expressed admiration for one predecessor in particular: William McKinley, our 25th president, who loved tariffs, and oversaw an expansion of U.S. territory around the globe. But McKinley is best remembered as being one of the four presidents that was assassinated, and for having his name attached to a mountain in Alaska. Correspondent Mo Rocca visits America's heartland in search of the legacy of the Gilded Age chief executive.