Born in Denver, Colorado, McKimson spent ten years getting an art education. He then went to work for Walt Disney. He stayed with Disney's studio for two years and then went to work for the Romer Grey Studio located in Altadena, California, a would-be animation shop started by the son of Western author Zane Grey, and financed by Zane Grey's wife. Several cartoons were animated at the Romer Grey Studio, but due to the ruin of Grey's fortunes after the Wall Street Crash of 1929, none were ever released. Most never made it to camera.