June 30, 1937 London, UK
The world’s oldest emergency telephone number 999 was introduced in London.
The number 999 may not be the best combination of numbers on the dialing board of a traditional telephone, but it’s still used in the UK.
Reference
- https://www.bbc.com/news/magazine-18520121
- https://en.wikibooks.org/wiki/First_Aid/Appendix_F:_Emergency_Telephone_Numbers
