This is a link to about 100 public domain newsreels produced by NASA,United Newsreel, and Department of the Interior. They range in length from 10-30 minutes. There's a lot of interesting stuff here. Examples include 1930s titles from the Dept of Interior, 1940s war newsreels, and "Who's out there?" a 1975 film narrated by Orson Welles on the likelihood of intelligent extraterrestrial life.