Hi All, I managed to track down a 1970 issue of The World Almanac & Book of Facts. On page 952: "Gradually replacing the traditional abbreviations for the states of the U.S. are the two-letter ones approved by the Post Office Department when it introduced the ZIP Code in [October,] 1963." Then followed a chart of the official two-capital-letter P.O. abbreviations. So... Who wants to define "gradually?" ;-) A Govt Docs librarian at I.U. found a reference to 2-letter abbreviations (BUT the example was "Va" NOT "VA" -- no period though) in a 1967 P.O. bulletin about the new OCR letter sorting machine. One person e-mailed the recollection of learning to address PA as "Penn." in high school in the mid-70s. Gradual, indeed. Chris Bobbitt [log in to unmask] Curator of Collections Monroe Co. Historical Museum Bloomington, Ind.