North American area codes are sometimes called NPAs, an acronym for Numbering Plan Area. This comes from the acronym NANP (North American Numbering Plan). If you have a relatively old area code--one with a middle digit of 0 or 1--it reflects the relative population of your area when the NANP first came into existence. Populous areas like New York (212) got "low dial-pull" numbers: ones that could be dialed quickly on rotary phones.