19631776 Club
Post Office rolls out five digits for every address in America
The Zone Improvement Plan assigns a unique ZIP code to each address nationwide, with the first digit narrowing a region and each that follows pointing closer to a single post office.
By the early 1960s, the postal system that had carried the nation through two world wars was straining under its own volume. Experienced clerks had been replaced during wartime by inexperienced workers who couldn't memorize every carrier route, and the old zone numbers used in large cities weren't keeping pace with a country that had sprawled into suburbs. On July 1, 1963, the U.S. Post Office Department rolled out the Zone Improvement Plan nationally — five digits assigned to every address in America, with the first narrowing down a region and each subsequent digit pointing closer to a specific post office. Within three months, postal inspector Robert Moon estimated the codes appeared on 30 percent of all mail…
