I can’t remember the specifics, but wasn’t there a cult in Oregon that had enough numbers to take over the local county government (sheriff, etc.), and the state government stepped in to stop them?
That would probably be Rajneeshpuram (sp?) that you are thinking of. I don’t know the details, but I believe the cult used methods such as spreading e coli via a Taco Bell salad bar, or something like that. That’s the sort of thing that tends to get the state involved.
In any event, if the 20,000 confined themselves to only a few of Wyoming’s legislative districts, they could probably get a foothold in the state legislature. Maybe that would be enough of a spur to get more people to move in, and start to get some legislation passed.
Vermont would also be a decent choice from the opposite end. You’d probably get decent support for drug law reform there, for example. And I believe it has some of the laxest gun laws in the country (IIRC, only state to allow concealed carry without a license).
I would be curious to see if such a state would even work. It’s not like they would be creating a Utopia or anything. All states have to deal with problems like crime, unemployment, infrastructure repair, and pretty much anything else you can think of. Libertarian or not, the people of a state will expect their government to address these problems. It would be interesting to see how they would do it.