An area code is a three-digit number used in telephone numbering plans to designate specific geographic regions. In the United States, area codes help route calls to the correct locations, making it easier to connect with people across different states or cities. Each area code corresponds to a particular area, which can range from a large city to a smaller region. Area codes were first introduced in the 1940s as part of the North American Numbering Plan (NANP). They are essential for organizing phone numbers and ensuring efficient communication. As the demand for phone lines increased, new area codes were created to accommodate the growing population and the rise of mobile phones.