Correct; that's the short answer; the following Wiki entry sums it up, but there's a lot more to it: http://en.wikipedia.org/wiki/Hermetic_Order_of_the_Golden_Dawn#Golden_Age

Despite the ill-will, Crowley celebrated his "birthday" (the date of his Golden Dawn initiation) throughout his life. Crowley started his own version of the Golden Dawn system - but firmly based in his philosophy of the New Aeon - called the A.'.A.'., which is distinct from the O.'.T.'.O.'.

Actually, here's a much better history from a LARP group:
http://www.vialarp.org/GD/background_5_detailed_gd_history.html

Considering the source, the top-level page is a good gaming resource (I forgot about this link - I would have put it in my OP):

http://www.vialarp.org/GD/

Sorry to cross-post, but this is pertinent to this topic as well:

I have an old Call of Cthulhu supplement called "Golden Dawn" (published by Pagan Publishing, not Chaosium), which gave an interesting twist on Victorian Era CoC gaming. I had adapted it for a Modern Era campaign some years back, and totally intend to adapt it to a Dresden Files campaign, in turn (or vice versa).

The premise that members, students, or other associates of such an occult fraternity would naturally be drawn into either a Call of Cthulhu or Dresden-type investigation is completely sensible, and this system gives PCs well-defined and specific advantages. As certain occult fraternities were represented at meetings of the White Council, such a Character base should fit easily into the Dresden universe

In real life, there are a number of Golden Dawn groups still in existence in many - if not most - urban areas (definitely in Chicago & Baltimore), as well as a number of other occult fraternities & initiatory societies (many of which adhere, to varying degrees, to the Golden Dawn system & curriculum). With Jim Butcher's well-defined rules, and well-reasoned descriptions, of how & why magic works, I've found myself wondering what, if any, familiarity he might have with groups like this (I have a few friends in Kansas City....).

With all this in mind, I'm posting the following link as a potential resource -- as I see that copies of the original supplement are fetching quite a price:

http://www.darkshire.net/jhkim/rpg/callofcthulhu/goldendawn/handout.pdf

I've been rereading the whole series the past couple of months, and the topic of this thread is EXACTLY what I thought of when I heard about a "mild earthquake" hitting Chicago last month. I'm surprised to not find it here!

http://www.chicagobreakingnews.com/2010/02/quake-like-tremors-reported-in-western-suburbs.html

http://www.nbcchicago.com/news/local-beat/Breaking-News-Earthquake-Shakes-Chicagoland-84000302.html