We count the states we've been in with the motorhome. You can get the maps at Camping World or most RV dealers. We put ours on the inside of the door so it shows while we are camping. (If the door's open). I have seen them on slide outs on the end facing the patio, so you see them when the slide is out. Just wherever you want to put it.
We add a state if we stayed the night with our RV. We don't count drive throughs. We also can't seem to manage WV, as you can see we circled Idaho too.