Charles F. Haanel (1866-1949) was an American author, philosopher, and businessman best known for his seminal work "The Master Key System." Born in Ann Arbor, Michigan, Haanel began his career as an office boy in St. Louis before becoming a successful entrepreneur. He founded the Continental Commercial Company in 1905, which grew into one of the largest conglomerates of its time, valued at $2.5 million.

His intellectual pursuits matched Haanel's business acumen. He was a 32nd-degree Mason, a member of various prestigious societies, and held honorary degrees in metaphysics and psychology. His philosophical interests culminated in the publication of "The Master Key System" in 1912, a course in New Thought and personal development that allegedly sold over 200,000 copies worldwide by 1933.

Beyond his most famous work, Haanel authored several other books on mental development and success principles, including "Mental Chemistry" (1922) and "The New Psychology" (1924). His writings have influenced generations of self-help authors and continue to be studied by those interested in personal growth and success.
Haanel spent his later years in St. Louis, where he passed away in 1949. He left behind a legacy as a pioneer in the field of personal development.