How do you identify a United States city phone code?

A United States city phone code, commonly referred to as an area code, can be identified online from various websites including Country Code. The area code is a three-digit number that is assigned to a specific area and is preceded by the number one and followed by the seven-digit telephone number when dialing outside of the area.

In order to identify area codes online:

1. Look up desired area code by city

Area codes are arranged either numerically or alphabetically by city. Lists can be found in phone books or online.

2. Determine city of an area code

If a cell phone or caller identification number originates from a certain area code, the area code's location can be found by the same means: phone book or online. The area code can also be entered into a search engine to obtain its origination.