when did modular phones appear?

[McHeath]

My folks place was not modularized until 1984, that was in Bakersfield California.  They came out and replaced all the phones in one fell swoop, leaving 2554s and 2500s in place of the oldies my folks had since the late 50's.  Sad day, I still recall not being happy about it and mom to this day wishes they had left her old phones in place. 

[AET]

My grandparents built their house on 60th st. in 1951 and my dad said growing up it was 4-prong and he beleives it was when they sold that house in 1987.