I once heard a British weatherman on BBC TV talking about the weather in Arizona around “Tuck-sun.” I bet the OP would have gone ballistic over that. 
I sometimes still use the traditional Ill. when I send cards. When I send them to relatives in Chicago, however, I no longer put the zone. I have progressed to zip codes!
Anyway, I too don’t have them all memorized. The traditional abbreviations are easier.
And don’t forget that both Canada and Mexico have two-letter postal abbreviations for their provinces and states as well. Canadian abbreviations are ‘compatible’ with US ones, in that they are different; Mexican ones overlap with US ones (and Canadian ones as well: BC = British Columbia and Baja California).
I always leave Arizona as [del]is[/del] AZ.
Never like the abbreviation for arizona that way either, I’ve always called it AZ.
Post #6. 
Although to your credit, you do have a cite.
Anyway, using AZ takes away a good pun.
I live in a town that’s so baseball-crazy, they named it Norunsnohitsno, Ariz.
Everybody from around here knows it’s “Too-stoned.” 
I dunno, Mich, Fla, Colo, Minn, Wis, Mass all come to mind.
Tell you what- get rid of Arpaio and we’ll talk about getting you some respect.
And then there was the time in a local paper when some editor, presumably a Brit, Anglicized the state’s spelling to Arisona.
Try living in Washington. Guess which one.
LOL! Was just going to post this. “No, the OTHER one”.
I’ve had their jelly. It tastes like crap, but goes down easy.
Cry me a river:
Thank you!
Actually, I should amend that, as some of the traditional shortenings are contractions and not abbreviations technically (like Fla. and Ga.)
<nitpick>
Sixth largest. Houston is the fourth.
</nitpick>
Australia has postal abbreviations, though a majority are three letters (ACT, NSW, QLD, TAS, VIC). So if you write “WA” in Australia, no one thinks you’re talking about Washington State – you mean Western Australia.
Born and raised in Cincinnati, O.; currently posting from Columbus, O.
Has anybody informed the OP, yet, that Houston is actually the fourth largest city in the US, not Phoenix?
Maybe he meant tallest?
Yes, “O.” is the traditional abbreviation for the Buckeye State, but it dates from the time when the land north of Texas was Indian Territory.