How are zip codes determined? Are they a derivative of latitude and longitude?
Preparing for the new system was a major task involving realignment of the mail system. The Post Office had recognized some years back that new avenues of transportation would open to the Department and began to establish focal points for air, highway, and rail transportation. Called the Metro System, these transportation centers were set up around 85 of the country’s larger cities to deflect mail from congested, heavily traveled city streets. The Metro concept was expanded and eventually became the core of 552 sectional centers, each serving between 40 and 150 surrounding post offices. Once these sectional centers were delineated, the next step in establishing the ZIP Code was to assign codes to the centers and the postal addresses they served. The existence of postal zones in the larger cities, set in motion in 1943, helped to some extent, but, in cases where the old zones failed to fit within the delivery areas, new numbers had to be assigned. By July 1963, a five-digit code had bee
