What the digits mean
ZIP stands for Zone Improvement Plan. The five-digit code was introduced in 1963 to speed up the sorting of mail.
- The first digit is a group of states, starting with 0 in the Northeast and rising to 9 on the West Coast.
- The first three digits together point to a regional sorting center.
- The last two narrow it down to a post office or delivery area.
| First digit | States |
|---|---|
| 0 | Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, Rhode Island, Vermont |
| 1 | Delaware, New York, Pennsylvania |
| 2 | District of Columbia, Maryland, North Carolina, South Carolina, Virginia, West Virginia |
| 3 | Alabama, Florida, Georgia, Mississippi, Tennessee |
| 4 | Indiana, Kentucky, Michigan, Ohio |
| 5 | Iowa, Minnesota, Montana, North Dakota, South Dakota, Wisconsin |
| 6 | Illinois, Kansas, Missouri, Nebraska |
| 7 | Arkansas, Louisiana, Oklahoma, Texas |
| 8 | Arizona, Colorado, Idaho, Nevada, New Mexico, Utah, Wyoming |
| 9 | Alaska, California, Hawaii, Oregon, Washington |
Puerto Rico and the US Virgin Islands also start with 0, and Guam with 9.
ZIP+4
The four extra digits, added in 1983, identify a smaller unit such as one side of a street, a single building or a group of PO boxes. You rarely need them, but they let mail be sorted more precisely.
A route, not a boundary
ZIP codes were drawn for delivering mail, so they do not follow city or county lines. One ZIP can cover parts of two towns, a large city has dozens, and some belong to a single building, a university or one organization. Others exist only for PO boxes. Statistics published "by ZIP code" usually use the Census Bureau's approximations, called ZIP Code Tabulation Areas.
What our lookup tells you
The ZIP code lookup uses the first three digits to find the state, its time zone and the area codes in use there. It runs in your browser and does not send the ZIP anywhere.