What year did the US implement area codes as opposed to local phone operators?

i found an old business card and the phone number is listed like this, PO.3-8506. is that the way phone numbers were when you had to ring up the local operator and have them put you through to whomever you were calling.What year did the US implement area codes as opposed to local phone operators?
No. You could dial a local number directly back to the 1940s or maybe sooner except for long distance. It was changed to all number system in the 1960s. We started area codes then too. During the time when you had to get an operator that was in the 1920s and earlier, or if you lived in a remote or rural area, you had to call Central operator to get a number. That was also before there were dials on phones. In the 1920s there were prefixes like PO but there were only 4 numbers after it, not five. The PO in your number became 76 later on. In the 1950s my family still had a party line. That was sharing a land line with another family because the technology had not caught up with the demand for phone numbers in the 1950s. We used phone operators to make collect or person to person calls until the 1990s I think.



Now with fax machines and cell phones, it definitely has to be like that plus having all the different area codes. We didnt have private fax machines until the 1980s and cell phones of course in the 1990s.