Willard Mullin was a fairly famous cartoonist. Below is a cartoon he did relating to the 1935 Kentucky Derby (May 4, 1935). My mom found this in a thrift store in the late '80s/early '90s in metro Detroit and gave it to me. This very large piece of art was scanned by Stephen Worth at the ASIFA-AHAA several years ago (there's actually a picture of he and Katie Rice looking at it while David Gemmel does something else on the main page of of the Animation Archive page).
You can see more on Mullin at Animation Resources: http://animationresources.org/?cat=461 http://www.animationarchive.org/?p=2184