During a casual glance at a map today my eyes fell upon Luzon, the main island of the Philippines. When I was growing up in Detroit, my grandmother's telephone was often given as "LUzon-5-1864" (or whatever the digits were; I'm sure my mom remembers). I never knew what it referred to. I also recall that "LOgan" was another common alphabetic prefix (and, admittedly, I might be mixing this up -- grandma's phone number may have been LOgan-something, but LUzon was definitely popular, too).
I got to thinking: what was up with the alphabetical prefixes? I assumed it had something to do with mnemonics, but was it a formal program supported by the phone company or was it just a popular practice amongst its customers?

