To sun it up from the NYTimes article posted below, Oklahoma does in fact have legal medical marijuana. In addition it apparently has pretty lax regulations compared to other states on growing. Basically little limit on how many farms are allowed, how much they can grow, etc. And apparently pretty low startup costs (I assume license fees and all that are low).

OK is as close to a free market as you can get, low license fees, taxes, etc. Recreational use is on the ballet for a special session in the spring and it’s already legal for medicinal use and a very liberal def. of “medicinal” at that. There are dispensaries everywhere.

/own 20 acres in SE Oklahoma (tangent, my property taxes last year was a whole $9)