If you're only going to see one movie from what I'm calling the pre- Oscars Silent Era, then Buster Keaton's masterpiece The General is the one to see.
Not only is it one of the greatest comedies ever made, The General, which Keaton wrote, directed and starred in, is also an action film that puts most of its modern counterparts to shame.
Based on an incident from the American Civil War, the story—about a lovelorn engineer who finds himself battling spies who hijack his train—features a spectacular chase involving two, then three speeding locomotives, daredevil stunts, explosions, burning bridges, comic mishaps, sight gags, split-second timing, all while Keaton woos the girl.
This being the real thing (Keaton did all his own stunts and used full-sized trains, one of which wound up sitting in the bottom of a river for fifteen years), it's a wonder nobody got killed filming it.
Like in the best silent films, the lack of dialogue is almost irrelevant. The outline of the plot is easy enough to follow: war breaks out and to impress the woman he loves, Keaton tries to volunteer. But as an engineer for the Western & Atlantic Railroad, he is more valuable where he is than in uniform, so the army's recruiters reject him.
Of course, the army doesn't bother to explain the situation to Keaton or to anyone else. The girl assumes he is a coward and the rest of this brief, 75-minute movie involves Keaton proving otherwise.
In case you're afraid you don't have the patience to sit through a silent movie, I can reassure you the set-up takes only 14 minutes before the spies to show up, hijack Keaton's train—which, by the way, was based on a real-life Civil War era steam locomotive named "The General"—and kidnap the woman he loves. Even then, Keaton has already treated you to one of the most famous sight gags in movie history.
From there, the story unreels at breakneck speed.
In addition to the two separate train chases that bookend the movie, there's time for a daring escape, a battle between the two advancing armies, and an endless series of gags. Keaton's famously understated reaction to the chaos around him—he was known as "The Great Stoneface"—only adds to the modern feel of the production.
In 1999, the American Film Institute ranked Buster Keaton number 21 on its list of the greatest movie performers of all-time; Entertainment Weekly listed him as the seventh best director; and Roger Ebert has written "Today I look at Keaton's works more often than any other silent films."
Watching The General again, it's easy to see why. I'm giving it the Katie-Bar-The-Door Award for Best Picture of the Silent Era.