North American Numbering Plan usually shown in capital letters, were dialed. Later, the third letter, where implemented, was replaced by a digit, or an extra digit was added. This generally happened after World War II, although New York City converted in 1930. The adoption of seven-digit local numbers (2L-5N) was chosen as the requirement for direct distance dialing and progressively deployed starting the late 1940s. The famous Glenn Miller tune "PEnnsylvania 6-5000" refers to telephone number PE6-5000, a number still in service at the Hotel Pennsylvania (212 736-5000) in New York. Similarly, the classic film "BUtterfield 8" is set in the East Side of
PEnnsylvania 6-5000 Hotel Pennsylvania, claims it to be the oldest continuing telephone number in New York City. While the hotel opened in 1919, the exact age of the telephone number and the veracity of the hotel's claim are unknown. At the time of Glenn Miller's popular network radio broadcasts, most local telephone calls in large cities were being dialed directly. All intercity calls required the operator. There were no area codes. The length of local numbers varied widely; four or five digits was more than enough for a small city with a single central office, while separate central offices served individual neighborhoods