Middleton's family was prominent in the San Francisco Bay Area and was involved in the Ocean Shore Railroad and Middleton Motor Car Co.[1] His father was a timber baron.
Middleton graduated from Lowell High School and joined the car business. He did advertising and promotion for the auto business including short films. He also made film promotions under contract for other businesses. He became an executive producer and director at CMPC, which he named. He also created the film company's logo with a bear on it.[1]