So to answer the second question first, as far as I can tell they don't split the state. There is only one California forum there.
As for the original question, based on the numbers, I would agree with you. I did an analysis of the numbers based on a discussion with
@Mockingbird , and based on my findings, California and the Midwest forums are the ones that would most benefit from splitting. I could easily split the latter into "Plains" and "Great Lakes" or something similar by assigning the member states to one or the other.
California would be more difficult though.
Yes, I could technically look up the latitude of the given site when I auto-create threads, but that ends up being far more work than the more elegant solution I have today, and it would be specific to California, which is problematic. Right now I have a simple table that maps state names to forum ids. I would need to actually write a function to do some calculations to determine which forum to use.
But an even larger problem is for people that are looking for or creating their own threads. Now they are going to have to determine which forum to look in, and at least for stations on the edge of the boundary you suggest, it may not be obvious which one to look at. And since my hope is that eventually the community will grow to a point where it's the community that first discovers future stations (rather than getting them after the fact), I hope that the predominant way threads are created is by the user community themselves. I foresee a lot of confusion and extra work maintaining the proper location of threads.
It's not that I don't think it's a good idea, it's just that it creates several problems that I don't think have easy solutions, so for now, I think I am going to pass on this idea.