In the larger populated cities of the time, merchants found a way to cater to busy customers who had little time or energy to prepare food during the evening. The variation in Chinese cuisine from different regions led caterers to create a list or menu for their patrons.
ZIP Code began on July 1, 1963, as scheduled. Use of the new code was not mandatory at first for anyone, but, in 1967, the Post Office required mailers of second- and third-class bulk mail to presort by ZIP Code. Although the public and mailers alike adapted well to its use, it was not enough.
On July 1, 1963, the Post Office Department implemented the five-digit ZIP Code, which was placed after the state name in the last line of an address. To provide room for the ZIP Code, the Department issued two-letter abbreviations for all states and territories. Publication 59, Abbreviations for Use with ZIP Code, issued by the Department in October 1963, told why.