uspsoig.gov

9wrd6 TIL that the Zip in Zip Code stands for Zone Improvement Plan, has been in use since 1963, and adds $10 billion annually to the US economy.
a8rJL TIL that US zip codes as we know it only started in the 60s
PYDLO TIL the USPS has a hotline (and email) for reporting fraud activities of its employees, which would include the postmaster general