Here's why '555' is always used for phone numbers in TV and movies

When TV shows and movies need to use a phone number as part of the story, they typically use one that starts with "555." We spoke with an official historian at AT&T to find out why these 3 numbers in particular were chosen. It turns out that the answer has a lot to do with the way telephone numbers evolved over time. Following is a transcript of the video.

Pick up your phone and call the professionals, Ghostbusters.

Narrator: Did you ever wonder why phone numbers in TV shows and movies always start with the numbers 555?

555-1125.

It's 555-3455.

555-2401.

Narrator: The short answer is that most 555 numbers are not working numbers, so real people won't be harassed if die-hard fans try to call them. - 55 was an exchange combination that was not used very often in the American telephone system.

You may get a wrong number or no number at all.

Narrator: An FCC contractor called the NANPA, or North American Numbering Plan Administration, is tasked with assigning numbers for use. 555-1212 is still used for Directory Assistance and 555-4334 is reserved for Assigned National use. But a set of one hundred 555 numbers have been officially designated for use in Hollywood, 555-0100 through 555-0199.

Cory Gillis, 555-0176.

Narrator: Back in the early 90s, 555 numbers outside that range could be reserved for information service providers, but this program was shut down by the NANPA in 2015. While those other numbers might one day be put back in circulation, the 100 reserved for TV and movies will not, so they will always be safe for use. So, how specifically did 555 become the famous number that it is today?

Decades ago, phone numbers used to look a lot different. They consisted of a word and a five-digit numerical code. The word was a telephone exchange name and the number was assigned to a specific phone in that area.

Sheldon Hochheiser: Up until 1919, all telephone calls were manual. You had to start by speaking to an operator.

This is WY 5-2240.

Narrator: References to this system can be seen in the names of movies, like BUtterfield 8. And songs like the Glenn Miller Orchestra's, PEnnsylvania 6-5000, which calls hotel Pennsylvania in New York.

Hochheiser: These were based on names that could be easily understood verbally. - Narrator: Eventually, phone companies switched to a system where customers had to dial themselves.

We are changing your telephone service over to dial. Take up your receiver and always listen for the dial tone.

Narrator: Phone numbers were reached using numbers corresponding to the first two letters of the exchange name. So, if you wanted to call Pennsylvania 6-5000, you would dial 73-6-5000. Since seven corresponds with PQRS on the keypad, and three corresponds to DEF. For Butterfield, you would start with 28. So, with this in mind, let's take another look at 555.

Hochheiser: Now, some combinations for the first two letters of a word worked better than others. One of the combinations that were very difficult to correlate to useful exchange names was 55.

Narrator: On the keypad, five has the letters JKL. Letters, which when placed next to each other, don't make many words or exchange names. So, there were not many real phone numbers starting with 55.

Hochheiser: Klondike, which has become well-known, is about the only one.

Klondike 4-2106, Los Angeles please.

Then call Klondike 5-3226.

Narrator: These numbers were often shortened to just the first two letters plus the five digit code. Since Klondike five was not frequently assigned, it found other uses. Bell systems noted in an official guide that the 55X exchange was reserved for radiotelephone.

The portable transmitting and receiving radio unit that makes it possible to combine radio and wire telephony for communication purposes.

Narrator: This was actually a very small group of numbers used in early mobile phones. Klondike 5 was also a sample number used in old phone company advertisements and it began to be used in old movies and TV shows. Eventually, area codes were introduced allowing for more available phone numbers and the exchange names were abolished, but the 555 trope is still used today in Hollywood.

What's the phone number of this store? - 555-2310.

Narrator: So, if you're looking for a Ghostbuster, who are you gonna call? No one.