Information, Area and Zip
Codes by State:

US Area Codes

In the United States as well as in Canada and Caribbean (24 countries and territories total) all telephone numbers are managed and allocated by North American Numbering Plan Administration. Particularly in the US, phone numbers administration is under the jurisdiction of Federal Communications Commission.

The Meaning Of Digits In A Phone Number

Each phone number in the US has 10 digits. The first three are known as NPA codes that are commonly called area codes. The next three digits are called the prefix of exchange, or NXX. Same as area codes, they determine a block of numbers for a certain location, and not all possible combinations are used. Since the number of landline phones, faxes and cell phones is constantly growing, some area codes may be added that means there can be two different area codes in one location (overlay).  

Area Codes Distribution

More than 300 area codes are used for geographic areas of the United States, while other 10 are not connected with geographical locations. They are round numbers like 500, 700, 800 (free toll calls when the called party is charged instead of the person who is calling), 900 and also 456, 710, 855, 866, 877 and 888. The state having the largest number of area codes is California with 30 telephone codes, following by Texas with 24 codes, and Florida and new York with 17 and 15 respectively. Some sparsely populated or small states like Alaska, Hawaii, Rhode Island, North and South Dakota, Montana and others have only one area code.  

How Many Phone Numbers Are There?

Taking into account that there are 10 digits in a phone number, there can be 10 billion subscribers. But according to the number of area and NXX codes that are currently in use, there can be only about 1.6 billion numbers for the entire North American Region. Still there is nothing to worry about, because with the existing population every person can have 4 phone numbers.

US ZIP Codes

ZIP Code Geography

Generally, ZIP codes are connected with state boundaries and geographical locations, but it is not a rule. For example, there are military ZIP codes (such as for the Navy), or special codes for large mail receivers. This happens because such measures help to increase mail processing efficiency, the main purpose of using codes.

Some rural areas may not have a certain code, such as in Utah or Nevada, where mail deliveries are rare or absent at all. The boundaries of a ZIP code may cross the boundary of the state or the county, so it is better to rely on USPS data rather than just looking at numerous maps.

The most frequently used ZIP code map is the one made by the Census Bureau, but still it doesn’t give entirely correct results. The regions on the map are called ZIP code tabulation areas, they determine the smallest units used by the census. There is an interesting point that one city block may partially refer to different tabulation areas.  

Modern usage

ZIP codes were introduced to ease the work of the United States Post Service, but now they are used by many other delivery companies such as UPS, DHL or FedEx. Thanks to the ZIP codes, companies can provide information about the shipping rates to your destination immediately. This is very useful for customers who are buying goods online, since they can quickly know the cost of delivery or find the closest dealers searching them by a ZIP code.

Today a 5-digit code is usually enough for most occasions. Modern mail sorting equipment reads data on the envelope and specifies the 9-digit code automatically.

How To Search Area Codes

The United States area codes database includes area codes of all telephone numbers listed in the white pages. If you know an area code, you can find where the number comes from, and knowing the entire number it is possible to find the exact location.

Area codes are grouped according to geographical or numeric order, so they can be searched by states or cities and also by numbers. It is also convenient to use a reverse phone number lookup that shows the subscriber's location and name after you type a telephone number.

ZIP codes are a system of indexes used by the USPS for increasing the efficiency of mail sorting and delivery. The idea of ZIP codes was suggested by Robert Moon in 1944 but was launched only in 1963. The name ZIP stands for Zone Improvement Plan, which optimizes routes of mail delivery.

ZIP Code Digits

At the beginning, there were 5 digits in the code, first three representing the sectional center (commonly called sec center) – the place where mail is collected and processed. A sec center sorts mail and sends it to smaller post offices according to the last two digits of the code.    

Starting from the early 80s, 4 digits were added to the standard index to form a ZIP +4 code. The additional information specifies the location of the delivery more precisely, as such it can be a city block or even a large individual receiver.