Back in April, I mentioned that as a result of my posting here, I was consulted for a non-spoilery plot point by Geoff Johns for "Legion of 3 Worlds". I had promised to tell you what that was once the series was over. It's not really anything major, though.
In January 2008 I got an email from Johns asking for a list of the members of the United Planets up to the original Crisis. In retrospect, he was apparently doing research on the UP scenes in L3W. Here's what I wrote back to him:
Of course you'd have to start with a question I'm not fully prepared to answer, but I'll have to be Clintonian in my explanation.
To the best of my (limited) knowledge, such a list has never been made public and put on the internet. If such a list had been compiled, someone from the fanzines Interlac, Klordny, or the Legion Outpost probably did it sometime in the last 30 years, but since those issues are all on paper, there's no telling unless someone has a complete collection.
That being said, there are some sources. In case you didn't know, in the late 1980s and early 1990s, Mayfair put out a bunch of DC role playing games, complete with various sourcebooks. The first two Legion books, 1986's "The Legion Sourcebook" and 1987's "The Legion Sourcebook vol. II: The World Book" contain RPG stats for pretty much anything Legion-related up to that time, which appears to be the time frame you're looking for. The World Book is most likely what you need, but of course it's one of the things that I don't have in my collection yet.
In 1990, Mayfair published the "Atlas of the DC Universe", which infamously places Metropolis in Delaware and Gotham City in southern NJ. The Atlas has a chapter that reprints some of the info from the World Book and says that most of the info predates the Great Collapse of 2989 (which was when Levitz left). The Atlas has info on 57 worlds, but that includes both UP worlds and others (the Dominion, Khundia, etc.). I can cull out the UP worlds from this list if you like.
For all their faults *cough*fanfic*cough*, the Bierbaums were great with detail. A planet mentioned in passing in an issue of Adventure Comics would become something important in their storyline, and their data was compiled in Mayfair's "2995: The Legion Sourcebook" from 1992. Helpfully, they even provided a map showing where the various planets were in relation to the Khundish Empire, the UP, the Dominion, the Dark Circle, and "hostile & unexplored". They list a total of 72 worlds, and elsewhere give the status of 76 worlds (some overlapping) and where they stood about a year into the v4 storyline. In giving the history of the UP, the book mentions that there were about 1000 worlds prior to the Collapse.
Now, if you don't already have these books, I can sift through them to get the UP worlds out. I also have an ebay bid on the World Book and the four game modules which is over tomorrow evening, so if I win that I can go through that book too.
Let me know what you'd like and I'll do what I can.
So it took me a little while to dig through those books. Here was my next note to him in Feb. 2008:
Finally got my Mayfair "World Book" in the mail today. Between that, the Atlas of the DC Universe, "Who's Who in the LSH", and Mark Waid's "Legion Index", I've come up with 182 named worlds.
I made some assumptions: basically unless we were told that it was not a UP world, that the UP couldn't interfere, or it was something like a planet inhabited only by criminals, I took it as a UP world. When Chameleon Boy turns into a Nitwonian Nibbybug, I assume that Nitwon is a UP world.
This list roughly coincides with the original Crisis or very shortly thereafter. The Index and the World Book came out in 1987, "Who's Who" in 1988, and the Atlas in 1990 (though it says that the data is pre-Collapse, which means it's good up through the end of the Levitz run).
The list does not include non-UP worlds, non-worlds (such as asteroids or space stations), or those worlds that lie within the UP space but are either destroyed or uninhabited.
Maybe for my next trivia quiz I should post the list of all 182 worlds I found and have you identify each one by issue and context.