State Abbreviations

The US Postal Service processes a lot of mail, and a human used to read every letter.  To expedite this, they preferred specific abbreviations.  Prior to 1963, they used relatively spelled out ones, as I've spelled them in the Abbr. column.  In 1969, they decided upon a new set of two letter abbreviations.  The only one that's changed since is Nebraska, which had initialy been NB.  Canada asked them to change, due to a conflict with New Brunswick, so they switched to NE.

The interesting thing was that there had already been a two letter naming system in place, for the registration numbers of boats.  Mostly, they're the same, but in 10 states, highlited in RED, they are different. 

Postal	Name	Vessel	Abbr.
AL	Alabama	AL
AK	Alaska	AK
AR	Arkansas	AR
AZ	Arizona	AZ	Ariz
CA	California	CF	Calif
CO	Colorado	CO	Col
CT	Connecticut	CT	Conn
DE	Delaware	DL	Del
FL	Florida	FL	Fla
GA	Georgia	GA
HI	Hawaii	HA
ID	Idaho	ID
IL	Illinois	IL	Ill
IN	Indiana	In	Ind
IA	Iowa	IA
KS	Kansas	KA	Kan
KY	Kentucky	KY
LA	Louisiana	LA
ME	Maine	ME
MD	Maryland	MD
MA	Massachusetts	MS	Mass
MI	Michigan	MC	Mich
MN	Minnesota	MN	Minn
MS	Mississippi	MI	Miss
MO	Missouri	MO
NE	Nebraska	NB	Neb
NV	Nevada	NV	Nev
NH	New Hampshire	NH
NJ	New Jersey	NJ
NM	New Mexico	NM
NY	New York	NY
NC	North Carolina	NC
ND	North Dakota	ND
OH	Ohio	OH
OK	Oklahoma	OK
OR	Oregon	OR	Ore
PA	Pennsylvania	PA	Penn
RI	Rhode Island	RI
SC	South Carolina	SC
SD	South Dakota	SD
TN	Tennessee	TN	Tenn
TX	Texas	TX	Tex
UT	Utah	UT
VT	Vermont	VT
VA	Virginia	VA
WA	Washington	WN	Wash
WV	West Virginia	WV
WI	Wisconsin	WS
WY	Wyoming	WY

https://about.usps.com/who-we-are/postal-history/state-abbreviations.htm