The history of the United States Post Office is filled with fascinating data and amusing facts. Remember that ZIP codes were made to make mail delivery easier. If it is more efficient for a mail carrier to drive across a state line to deliver mail, the ZIP code "boundary" will cross the state lines. And how does the United States Post Office use them? All mail with the same first 3 digits is first delivered to the same sec center where it is sorted according to the last 2 digits and distributed to local post offices.
ZIP Code Database
Postal Service, available for immediate download, and free monthly updates. When you download our U. Our zip codes database has the most comprehensive and precise data that you will find. You can perform free database lookups on our website with our software or you can download our ZIP codes database for data manipulation. Today, over ,, pieces of mail are delivered each business day, and our mail can take as little as one day to reach its destination. Back in , it could take three weeks for a letter to travel from Lexington, Massachusetts to Philadelphia, Pennsylvania.
The cost of mail was relatively much higher back then. It cost twenty-five cents to send a letter miles — not much less than it costs today to send a letter anywhere in the country, and in considerably less time!
Today, many of us in the United States expect to have our mail delivered to our homes and offices at no extra charge. Before July 1, , city residents had to pay to have a postal worker bring their mail to them; rural customers had to travel to pick up their own mail for another 30 years. Zip codes wouldn't have helped much in those days. Many famous Americans have been postal workers.
Truman was postmaster of Grandview, Missouri for a time. Perhaps the most romantic era in our United States postal history is that of the Pony Express. Before then, stagecoaches took more than 20 days to deliver mail from coast to coast.
In , William H. Russell bought strong horses and put a listing for good horseback riders in newspaper ads that read: The sec centers are not open to the public and usually do most sorting overnight. As you can see from the map of the first 3 digits of zip codes , the digits after the first are also generally assigned from east to west.
In the map, 0 is closer to white and 9 is much more vivid. It's easy to follow the gradient across each of the zones even though there are a few exceptions such as the southwest tip of Georgia which uses 39XXX like central Mississippi. Despite the fact that ZIP codes seem to be geographic in nature, that wasn't their intended purpose. They are intended to group mail to allow the USPS to deliver mail more efficiently.
Some ZIP codes will span multiple states in order to make mail routing and delivery more efficient. In most cases, addresses in close proximity to each other are grouped in the same ZIP code which gives the appearance that ZIP codes are defined by a clear geographic boundary. However, some ZIP codes have nothing to do with geogaphic areas. When ZIP codes appear to be geographically grouped, a clear shape cannot always be drawn around the ZIP code because ZIP codes are only assigned to a point of delivery and not the spaces between delivery points.
In areas without a regular postal route or no mail delivery, ZIP codes may not be defined or have unclear boundaries. The main issue is discussed above: The Census Bureau and many other commercial services will try to interpolate the data to create polygons shapes using straight lines to represent the approximate area covered by a ZIP code, but none of these maps are official or entirely accurate.
They provide a very close approximation of the area covered by a ZIP code. You can easily notice some of the boundary issues when viewing our maps. Very rural areas aren't labeled as belonging to a ZIP code such as much of Nevada and Utah where there are few, if any, addresses to deliver mail. If the address is on the same street as a ZIP code boundary on the map, be sure to search for the full street address to determine the ZIP code instead of relying on the map.
Their purpose is to convey statistical data about regions that are familiar to most citizens. As discussed above, it is difficult to precisely define a geographic area covered by a ZIP code.
ZCTAs were developed to account for some of the difficulties in assigning an area to a ZIP code and to precisely define a geographic area. In general, they are updated once every 10 years for the Census. The Census assigns an area to a ZCTA according to census blocks the smallest geographic unit used by the census. Imagine a city block that makes up a typical census block as pictured to the right. It is bounded on all 4 sides by portions of city streets that each have their own name and addresses.