three decades. take a look. in 34 years, 5,914 shows and almost 6,000 shows, ladies and gentlemen. reporter: he started off making $1506 a week as a weekend weatherman and booth announcer. but his stand-up comedy help land him his own late night show on nbc working in the shadow of the great johnny carson. and while johnny paraded out the stars, letterman made his name being off-beat. we are going to pull out here for station identification and get the host whoa. reporter: johnny carson throne of the tonight show was passed on to jay leno forcing letterman to cbs and a late night rivalry was born. just how pissed off are you? reporter: letterman carved out his own unique niche. his signature top ten countdowns and spared no one. number nine! what is up, gangsters?