Here is a really good Donald Duck cartoon from 1940, directed by Jack King. It features some beautiful animation by Ed Love and Emery Hawkins. The mine cart chase is wonderfully executed.
I also scanned some of the storyboard from this cartoon (art by Jack Hannah and Carl Barks) for your enjoyment. Hannah did the ones that look a little more refined, while Barks did the looser, cartoonier drawings. Absolutely inspirational!