I remember having a 6 digit phone number as a kid in Mexico. That how small my town was.
Discussion
The US used to have 5 digit numbers and then in the 1940s they added letters at the beginning to expand them. So if your number was 8-5409 you’d be given a prefix based on where you lived. In NYC if you lived in Murray Hill you’d get MH7-5409. Later it would just be written as 647-5409 but I knew older people who still only referred to it with the letter codes.
Oops MH8-5409
This system of telephone numbering was known as the North American Numbering Plan (NANP), which was first implemented in 1947.
Early phreakers used to be able to make the click sounds the systems listened for to spoof long distance dialing codes. Usually it required audio equipment but I seem to remember hearing stories about people who could just make them using their mouths.
Yes, blue box by Woz and Steve Jobs.