WGN Television, whose call letters are derived from the Chicago Tribune's first slogan, "World's Greatest Newspaper", hit the airwaves on April 5, 1948. "Not long ago, people said it couldn't happen," the Trib noted of the station's debut. "But last night, with the speed of light, a stellar program was flashed in all its sparkling beauty to screens as far away as 45 miles." Colonel Robert McCormick led the Tribune Company into the TV era, which would bring viewers such treasures as "Bozo's…