AT&T - the American Telephone & Telegraph Co. - was incorporated on 3 March 1885 as the long-distance division of American Bell Telephone Company. By the end of 1899, it had become the head of the Bell System.
On 25 January 1915 Alexander Graham Bell, who was in New York, dialed up Thomas Augustus Watson in San Francisco in that now famously historic call.
The postcard (seen here) depicts Santa on the phone and the front reads: Christmas Shopping Simplified by telephone Use the Bell.
It was around the middle of the 20th century that extensions came out and were available to the general household. The back of the above card is not a post card to send friends and family well wishes but rather an advertisement of the extension phone!
Can you imagine what a big deal an extension would have been then?
My Baba (grandmother) once told me a story of when she went into labor with Daddy. My grandparents were not well off. In fact, they had no car or phone when my Dad was born in 1942. She went into labor and my grandfather had to run to a nearby house that had a phone so he could call someone. Ironically, I cannot recall them ever not having an extension. One phone was downstairs on the desk in the living room and the other was upstairs at the top of the steps.
I do not recall my mom's parents having an extension line in the house. However they had a party line! No one else ever used the line ... except one day ... the day my grandmother passed away. My uncle and mom both did not ever recall someone else being on the line ever. It was probably the first chance this other woman finally got to chat on there! She was very pleasant about it when we explained why we needed to use the phone that day. I wonder if they even offer party lines anymore.