The oldest known telephone directory was issued in February 1878 and consisted of a single piece of cardboard. It listed 50 individuals or businesses in New Haven, Connecticut that had telephones but not their numbers. – WTF Fun Facts
1878
WTF Fun Fact – Ahoy!
People didn’t always say ‘hello’ when they answered the phone. When the first regular phone service was established in 1878, Alexander Graham Bell suggested answering the phone with ‘Ahoy!’ – WTF Fun Facts
Source: https://www.nytimes.com/1992/03/05/garden/great-hello-mystery-is-solved.html