IMDBwhacking
Maybe everyone else knows this, but I just realised that the movie IDs at IMDB are in rough chronological order. Movie 0000001 is Carmencita, starring Carmencita as herself. (IMDB's users have given it an average rating of 5.4/10.) All kinds of 19th-century shorts are down there in the single- and double-digits.
Will:
1894. I didn't realize they had discovered motion by that point.