The 400 Area Code Explained

In the article, you will learn all about the 400 area code and what it means to you. For instance, did you know that just over a million people have the area code?

History of the 400 Area Code

The 400 area code was created on March 11, 1959. It originally covered the entire eastern United States. However, in the early 1990s, the number of calls being placed in this area code began to increase significantly. This led to creating new area codes, including 617 and 858.

Nowadays, the 400 area code is primarily used for calls within New York City and its surrounding suburbs. It is also used for calls to Bermuda and parts of Canada.

What is the 400 Area Code?

The 400 Area Code is a regional code for the eastern half of the United States, including all of Maryland, Virginia, West Virginia, and Washington. This is also the area code for parts of Pennsylvania and Delaware.

The 400 Area Code was split from the 310 Area Code in 1997. The reason for the split was that there were not enough telephone lines to support both area codes.

People living in this area should not have any trouble using the phone, but they may experience longer wait times when making calls.

Location and Timezone

The area code is a part of the telephone numbering plan that allocates telephone numbers to geographic regions in the United States. Each area code is assigned a three-digit number. The first two digits are the regional code and the last digit is the local code.

The area code for Los Angeles is 310. The 310 area code covers most of Los Angeles County and parts of Ventura, Orange, San Bernardino, Riverside, and San Diego counties. The area code for San Francisco is 415. The 415 area code covers most of San Francisco County and parts of Marin, Sonoma, and Solano counties.

Each telephone number in the United States must be within one of these area codes. If a number is not within an area code, it must be dialed using a long-distance prefix (800, 877, 866, or 1-800-555-1212).

Stats from Search Engine Result Pages

Area codes are one of the most common types of telephone numbers in the United States. They are also one of the most confusing.

There are currently ten area codes in the United States. Each area code is divided into several smaller regions. For example, the area code for Los Angeles is 323. The 323 region includes parts of Los Angeles, Ventura, and Orange counties.

When someone makes a phone call, they first dial the area code. Then, they dial the number within that area code. If the number is within the same region as the caller’s phone, the phone will automatically route the call to that number. If the number is not within that region, then the phone will look up the number’s location using a search engine and route the call to that number.


Area codes are a necessity for many people in the United States. They allow us to easily identify telephone numbers across vast distances and make it possible for us to communicate with people we might not be able to reach directly.