Robert Bringhurst’s book The Elements of Typographic Style is overwhelming me with typography details. Today I came across a description of using small caps for abbreviations, which inspired me to come up with this snippet for state abbreviations.
For abbreviations and acronyms in the midst of normal text, use spaced small caps
Many typographers prefer to use small caps for postal abbreviations (San Francisco, CA, 94119, and for geographical acronyms longer than two letters. Thus, the USA, or in Spanish, los EEUU, and Sydney, NSW.
The Elements of Typographic Style – Robert Bringhurst page 48