I found a fun site where you can select the states you’ve been to and a map is produced. Of course I am a little technically challenged, so I was unable to get the code and put up a better copy of it here, but I did save the image to my computer and used that here instead.
At any rate, I have been to 25 of the 50! Fun! I can’t wait to check out the other 25… especially the northeastern seaboard.