Did that change when your sister was born? How did they do it when she was born, and how many years apart were your births?
Not wanting to snoop or anything... ;)
My sister was born 3 years earlier (1965) in El Paso, TX.
The local newspapers just put it in automatically. It didn’t cost anything.
(My parents were really frugal. Something like a newspaper announcement was extravagant to them if it cost money)
My birth in Honolulu was not recorded in the newspapers. Of this I am 99% positive. My parents would have found it and but it in my baby book.