According to L Ron Hubbard Jr, his father said that Scientology actually began on December 1st, 1947 — the day Aleister Crowley died.
Rose Cross of the Golden Dawn and the Scientology Cross:
According to the Encyclopaedia Britannica:
a religio-scientific movement developed in the United States in the 1950s by the author Dianetics, a form of psychotherapy originated by Hubbard and later incorporated into Scientology.
John Parsons “worked” with Hubbard during the time he was crafting Dianetics in the late 1940’s.