- The Post Office relies on the ZIP code for prompt, efficient mail delivery. Each area of the country has a ZIP code. The East Coast ZIP codes start with ones; the Midwest ZIP codes start with fives or sixes; and the West Coast has ZIP codes beginning with nines. When an automated postal machine creates a stamp, it asks for the ZIP code to set the price. The stamp label even contains the ZIP code in barcode form. Even without needing to read the destination's city and state, the ZIP code is enough information to move the mail to the right place.
- Whether the mail is dropped into a mailbox on the corner or posted at a post office, the first thing that happens is to determine, by the ZIP code, if it is being sent locally or out of the area. Local mail goes into one tray to be sorted into individual routes according to the street address on the envelope. Then it is given to the letter carrier, who is responsible for that route to deliver personally.
- Any envelopes with ZIP codes from other post offices have to be routed to their proper destinations. First, they are separated into batches and put in trays. Each region of the country has a postal distribution center that further sorts and routs mail that is destined for several neighboring ZIP codes. The postal worker who receives the mail sends each batch as quickly possible to be transported to the correct distribution center. The process of sorting, removing local mail for local delivery and correctly and promptly routing the remaining mail until it is at its destination repeats until the mail is delivered.
