Do you contract the Postal code IN for Indiana if it is not followed by punctuation? Years ago, there was a rule that you did not contract any state abbreviations, but I cannot find the rule now.
The postal code for Indiana is abbreviated as IN. Abbreviations in general consist of letters. The rules tell us that when letters within an abbreviation that would make up a contraction are pronounced as letters, the contraction is not used. State abbreviations are pronounced as letters so no contractions would be used.