Federal Information Processing Standard state code
FIPS state codes were numeric and two-letter alphabetic codes defined in U.S. Federal Information Processing Standard Publication ("FIPS PUB") 5-2 to identify U.S. states and certain other associated areas. The standard superseded FIPS PUB 5-1 on May 28, 1987, and was superseded on September 2, 2008, by ANSI standard INCITS 38:2009.
Source: Wikipedia — Federal Information Processing Standard state code (CC BY-SA 4.0)