New York’s oldest still working phone number belongs to the Hotel Pennsylvania.

Looking nothing like the digit sequence we use today, Pennsylvania 6-5000 was immortalized in a song by Glenn Miller and his Orchestra, harkening back to the days when New York phone numbers used the name of its nearest telephone exchange. The famous number is still in service.

The Pennsylvania was designed by Manhattan’s leading architects McKim, Mead & White, and opened its doors in 1919. In the early 1930’s, it was given the phone number “PE6-5000”— in today’s phone parlance the letters P and E become 7 and 3 respectively, giving it the number 212-736-5000. Still in use today, it’s the longest continually operating phone number.

Until 1928, the Pennsylvania was the largest hotel in the world—with 2,200 lavish rooms, it was the height of luxury, and contained everything from a dentist to a fully-functioning hospital. Run by Ellsworth Statler (who lived in a private suite in the hotel where he would die of old age) the hotel was a byword in New York decadence.

The hotel’s magnificent restaurant and dance floor Cafe Rouge hosted some of the biggest swing bands of the era, including Count Basie, Duke Ellington and Glenn Miller who held a residency there from 1940-42. In 1940, Miller’s orchestrator Jerry Gray wrote the song which would enshrine the hotel’s phone number in popular culture. As recently as 2012, callers to the hotel would hear the tune until the operator answered.

Today the Hotel is in a somewhat sorry state, eclipsed by luxury hotels like the St. Regis and the Waldorf Astoria. Sadly, the Cafe Rouge is no longer in use and is inaccessible from the hotel. This once fabulous venue is occasionally hired out for one off events such as New York’s fashion week, or recently a Michael Jordan shoe launch, but largely sits empty and abandoned. As recently as 2013 current owners Vornado Realty had plans to demolish the historic building.

But despite its faded glamour, it is still possible to walk in the footsteps of Glenn Miller through the hotel lobby to the house phone and give your number as Pennsylvania, Six Five Oh Oh Oh.