The history of the movie trailer APR 03 2014
Filmmaker IQ has a nice exploration of the history of the movie trailer. And yes, they actually used to play at the end of (i.e. "trail") the film.
Coming into the 1960s, a new generation of star directors began to redefine the trailer - among them was the legendary Alfred Hitchcock. Instead of showing scenes from the movie, Hitchcock, who had become quite well known to audiences from his "Alfred Hitchcock Presents" TV series, cashed in on his celebrity... taking audiences on a tour using his gallows humor style in this trailer for 1960's Pscyho.
The reemergence of Cubism in film and commercial art in the 1960s was not lost on another emerging filmmaker - Stanley Kubrick. Having experimented with fragmented cutting styles in the trailer to 1962's Lolita, Kubrick comes back strong in 1964's "Dr. Strangelove" with a trailer that I consider one of the most bold and brazen pieces of movie advertising ever made.