Prior to 1973, cards were issued in local Social Security offices around the country and the area number represented the office code where the card was issued. This did not necessarily have to be in the area where the applicant lived, since a person could apply for their card in any Social Security office. Beginning in 1973, when the SSA began assigning SSNs and issuing cards centrally from Baltimore, the area number was assigned based on the ZIP Code in the mailing address provided on the application for the original Social Security card.