These are all zip codes for Chicago, not including the Chicago suburbs. Can you imagine delivering to mail without having the ZIP code? ZIP codes didn't even exist until 1963.
These are all zip codes for Chicago, not including the Chicago suburbs.
Can you imagine delivering to mail without having the ZIP code? ZIP
codes didn't even exist until 1963.
Between 1930 and 1963, there was a decrease in mail being sent. Fewer mail trains were making fewer stops. But there was also a change in the type of mail that was being sent. It shifted from mostly personal letters to business mail. By 1963, eighty percent of the mail was from businesses. This was caused by the shift from an agricultural society to an industrial society, as well as the invention of the computer. The computer was the single product most responsible for changing the makeup of the mail because the computer encouraged more companies, such as mortgage companies, banks, advertising companies, insurance companies, credit card companies, department stores, and more to send mail. By now, the volume of mail had increased.
The Advisory Board of the Post Office Department realized it was time to use a coding system because of the change in character of the mail, the increase in mail volume, the revolution in transportation, and the higher cost of manpower. They announced that the ZIP Code system, which is abbreviated for Zoning Improvement Plan, will begin on July 1, 1963.
Putting the ZIP code into effect meant some structural changes were necessary. Focal points for air, highway, and rail transportation, called Metro Systems were established in 85 of the countries biggest cities. This was expanded to create 552 sectional centers, each of which served anywhere from 40 to 150 post offices in the nearby area.
Next, Codes were created. By July 1963, every address in American had a ZIP code. The first number represented the general location in the country, ranging from 0 in the northeast, to 9 in the far west. The second two digits distinguished the heavily populated concentrations, whereas the final two digits designated smaller post offices.
By 1967, the Post Office required all mail to have a ZIP code.
Sources:
http://www.usps.com/history/his2_75.htm#ZIP
http://www.schlesingerassociates.com/zipchi.html