I found this video over at American Memory, a Library of Congress website that "provides free and open access through the Internet to written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music that document the American experience. " It's a 30 second film called "The Ball Game" that was produced by Thomas Edison in 1898. According to the American Memory website, "The Ball Game" was "(photographed) from one camera position behind home plate...(and) shows a baseball game in progress." Baseball Almanac states that the game was between two amateur teams from Newark, New Jersey.
You can download a better version of the film here.