Off the top of my head: HI, UT, AZ, TX, OK, AR, MS, WI, OH, FL, GA, SC, NC, VA, MD, DE, PA, NY, WV, RI, CO, and KY (22) so far, but I've had 55 years to do so without trying to play in all 50. Toughest is probably going to be AK, since it's a bit of a haul to get there during golf season. May have to make a west coast swing at some point to pick up CA, OR, WA, and NV and possibly ID.
By the way, Tar Heel, last time I looked Canada and Mexico were not among the 50 states.
Oops, somehow I omitted Wyoming as one of my states, even though I had posted a review under travel last summer of the Three Crowns GC in Casper, WY. (NOTE: I posted this earlier as a separate entry, but do not see it anywhere int he thread. Thus, I have added it to my original post. TH: I, too, have played in Canada but not in Mexico. I have, however, played in England, Germany, Saudi Arabia, and Bahrain.)