I think way back when in the day when I was knee high to a grashopper, 3 letter (or more) state abbreviations were normal. Cal., Nev. Ore., etc. Then the post office decided it would be more accurate with 2 letter abbreviations. I think they were trying that in the late 50's or early 60's. One of my teachers who was teaching us how to address an envelope (yes, they actually did teach usable things back then) was dead set against it. Then zip codes came out in the early to mid 60's. Then there wa MI MS MO MD and a few other. As well as Ak and AL. Thanks, Post Office and Postmaster General, where ever you are.