Zip Code stands for Zoning Improvement Plan. The introduction of the Zip Code became imperative after the volume of post increased phenomenally. Even during the 1930's , the time around which the volume of post underwent a big upswing in numbers, the bulk of post used to be ferried by the railways. Thousands of trains used to criss-cross the length and breadth of the United States to deliver mail to cities , towns and villages. It was long after in the year 1963 that the idea of the Zip Codes took shape. However the period through 1930 to the 1960's saw the peak of the railroad system which gradually declined. In the 1960's fewer trains carried post . Through this period the United States went through the great depression and the Second World War. The years hence saw the US transforming itself from an agriculture based economy to an industrialized one of great global importance. With this the business of transporting mail also changed dramatically.
In the 1960's the volume of mail went up substantially with the majority of it being composed of business mail. As the industrial expansion surged forward so did the volume of mail. The advent of the computer meant larger volumes of utility bills, bank deposits, magazines, credit card transactions and the like. The time was ripe to create a method by which the delivery of mail could be faster.
The postal department was working on a plan which could ease mail delivery. The thought of introducing a coding system had been hanging fire for well over a decade. Finally in the year 1963 the Zip Codes by city system was announced. This consisted of a five digit code which made it easier to dispatch mail to different locations around the United States. The first digit started from zero for the Northeast to 9 for the far West. The mail delivery system was all set to undergo structural changes.