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.
ZIP Code. 1  During World War II, thousands of experienced postal employees left to serve with the military. To offset the loss, in May 1943 the Post Office Department began a zoning address system in 124 of the largest cities. 2  Twenty years later, the Department implemented an even farther reaching plan, the Zoning Improvement Plan (ZIP) Code. The social correspondence of the 19th century had given way, gradually then explosively, to business mail. By 1963, 80 percent of all mail in the United States was business mail.