The history of phone area codes in the United States began in 1947 when the American Telephone and Telegraph Company (AT&T) introduced the North American Numbering Plan (NANP) to streamline and standardize telephone communication across the country. Before area codes, long-distance calls required operator assistance, making the process slow and inefficient. The NANP divided the U.S. into geographic regions, each assigned a three-digit area code, allowing direct dialing for long-distance calls. Initially, large metropolitan areas like New York City (212) and Los Angeles (213) were assigned easily dialable codes due to the prevalence of rotary phones. As the population grew and phone usage expanded, additional area codes were introduced, including overlays and area code splits, to accommodate the rising demand for phone numbers. Over time, area codes became an essential part of U.S. telecommunications, supporting the growing use of landlines, mobile phones, and fax machines.