With the large increase in mail volume that the Post Office Department had to deal with every year, the Department was constantly seeking ways to be able to better cope with this issue. One strategy of the Post Office Department used to quicken the processing and delivery of mail was to get the cooperation of the public to make delivery more efficient. Two ways the Department was able to get public cooperation were through presorting the mail and through use of the ZIP Code.
The Post Office Department needed the cooperation of large mailers if presorting mail was going to succeed. The POD first asked large mailers to voluntarily deliver their mail to the post offices at regular times to help control the flow of the mail through the facilities.(1) If mailers complied with this request, mail processing could be spread out through a 24-hour period, speeding up general processing times. Large (and even small mailers), could also help the Post Office by doing a primary sort of local mail and out-of-town mail to help the Post Office Department handle the mail more efficiently by spending less time sorting the mail.
The Department tried three main methods to try to encourage people to make an initial sorting of their mail. Mailing racks were installed in post offices so that patrons could place mail into either the local mail sack or the out-of-town mail sack. Letter boxes which had slots for local and out-of-town mail were placed in heavy mail traffic areas. Lastly, labels were made for the large mailers to identify their mail. Such labels were frequently used, and helped speed the mail.(2)
The Zoning Improvement Plan [ZIP] Code was introduced so that the Post Office Department could more efficiently sort the mail. In 1943 the Department had introduced its first numbered zoning system in order to simplify mail processing at a time when large numbers of postal employees had left the Department for the military.(3) The system, which was put into use on July 1, 1963, was initially designed primarily to use the cooperation of large quantity mailers and electronic data processing equipment to allow easy application of ZIP Codes to mail.(4)
An interesting issue that came up with the usage of ZIP Codes was the abbreviations for town and other location names. After spaces required for ZIP Codes, automatic data processing machines only had 13 characters left for town names, which led to more standardized abbreviations.(5)
Along with the development of the ZIP Code itself, the Department was dedicated to the development of machines that would be able to read the ZIP Codes. This research was done in coordination with development of optical character readers.(6) In 1965 officials hoped to have machines that would be able to read ZIP Codes and sort the mail at rates of approximately 36,000 pieces of mail per hour.(7) These machines would not only be able to do a primary sort based on ZIP Code, but if needed, could also read the town name and state to further sort the mail more precisely based on destinations. The ZIP Code was not only used for optical recognition. Studies were done with voice recognition sorting by workers operating parcel sorting machines.(8)
ZIP Codes were able to augment the increases in efficiency that were already becoming apparent with the use of machines. The Cost Analysis Division reported that “In addition to mechanization, ZIP Code presort of second and third class mail is expected to develop an annual savings approximating $35 million.”(9) The Department initially had a hard time convincing people to use ZIP Codes, and had to launch a national campaign to educate people about ZIP Codes, which included posters, songs, and advertisements about the system.