US Zip codes are a unique code used by the US Postal Service to help sort and deliver mail more efficiently. The term ZIP is an acronym that refers to the Zone Improvement Plan and consists of a 5-digit number that helps postal workers to quickly determine exactly where a specific letter or package is going. The system was implemented in 1963 and has been adjusted only once when they added the +4 to the code. The extra 4 digits helped the USPS to be more precise in sorting mail for delivery. While the code was specifically used for the postal service other courier services are now also using the new ZIP+4 codes to speed up their business as well.

This is because the USPS has made Free US Postal ZIP Code Lists available to the public. These lists help those who want to send mail through the postal service to look up the exact ZIP+4 code they need to use to speed up the delivery of their mail or packages.

Where To Find ZIP Code Lists:

There are several ways to look up the exact ZIP+4 codes when you need them. The easiest and most practical way is to use the Internet. Simply go to USPS's website and find the ZIP Code Look-Up page. There you will find a short and easy form to fill out. Fill in the company name (if needed), the address, apartment or office number, the city, state, and the 5-digit ZIP Code, and it will quickly look up the ZIP+4 for you. It's easy and takes only a matter of seconds. It will even give you detailed mailing specifications for the address including sorting codes, lot numbers, and postal mailbox numbers if you need them.

Understanding The Numbers:

The numbers in the ZIP+4 are not just random numbers assigned to certain locations – each digit has a specific purpose. The first digit indicates a region within the US that encompasses a group of states, the second and third digit determine the processing facility within that region that will receive the mail first. And the last 4-digits in the primary 5-digit code represent the local post offices where the mail will go through its final sorting before being delivered to its destination.

The new free US Postal Zip Code Lists now include the additional 4-digit codes to help postal workers find which city block, office building, or apartments the address may be located in.

Many people request a US ZIP Code Map for easy reference but considering the amount of detail that is included in the code it is not possible to create a map that can contain all the necessary information. The USPS does not have an official map that can accurately show all the ZIP details you need to look up. Other agencies have tried but there is no guarantee that the information provided is accurate and up to date. If you need to look up the new code, the best way to do this is with the free US Postal ZIP Code Lists already found online.