In the United States, there are more than 300 geographical area codes. Phone numbers represent regions; therefore, you can quickly pinpoint the location of a caller by looking up the area code. Most smartphones list the state that correlates with the area code already. But, if you're using a landline or want to know a more specific location, you'll have to resort to looking up an area code. You can do a basic search of the area code using your favorite search engine or use an online tool like All Area Codes. The latter will let you search by area code or city and state.