A native of Colorado, Propst began his career in the late 1940s as a graphic artist, teacher, and sculptor. In 1953, he formed the Propst Co., a Denver-based firm specializing in speculative product development. In other words, Propst drew on his independent nature and impatience with the status quo to attack problems, whether anyone asked him to or not. He called on Herman Miller with one of those speculative developments—a unique fishbone connection system for furniture components. Propst then signed on as a Herman Miller consultant and began conducting unprecedented studies of people in work situations as a basis for extending the company's line of products.
In 1960, Propst became president of Herman Miller Research Corp., where he continued investigating how the world of work operates, concluding that "today's office is a wasteland. It saps vitality, blocks talent, frustrates accomplishment. It is the daily scene of unfulfilled intentions and failed effort."
With over 120 patents under his belt, Propst continued his relentless investigations until his death in 2000.