Charles F. Haanel (1866-1949) used the concepts and methods found in
The Master Key System to create a successful business career in St. Louis,
Missouri, where he eventually founded one of the largest conglomerates of his
time. He wrote several bestselling books focusing on his business technique.
Besides The Master Key System, he also wrote Mental Chemistry and
The New Psychology. Known as the "father of personal development,"
Haanel's commonsense wisdom has revolutionized conventional thought for almost
one hundred years.