The reason some big online providers (some or all of, for example: AOL, CompuServ, Prodigy) had so many local access numbers (which was important since long-distance was so expensive) was that those numbers were actually Telenet / Tymnet, which the client used to connect to the service.
Connecting to the web via dial-up AOL looked (maybe still looks?) like:
AOL's seekrit superpower when they were "$CITYNAME Online" for several values of $CITY, as i was told, was that they ran on a big insurance company Stratus cluster as a slack time job and had access to both the compute time and the inbound X.25 for "free" for a while there.
For the uninitiated: https://en.m.wikipedia.org/wiki/Telenet
Another big one was https://en.m.wikipedia.org/wiki/Tymnet
The reason some big online providers (some or all of, for example: AOL, CompuServ, Prodigy) had so many local access numbers (which was important since long-distance was so expensive) was that those numbers were actually Telenet / Tymnet, which the client used to connect to the service.
Connecting to the web via dial-up AOL looked (maybe still looks?) like:
Browser <-> HTTP(S) <-> (I forget this component) <-> AOL client <-> Modem <-> PSTN <-> X.25 <-> AOL backend <-> HTTP(S) <-> Website
Is the part that I’m forgetting SLIP/PPP? I forget how that was implemented in Windows… Possibly both the browser and the AOL client talked to that.
(That was all after you could use AOL for TCP/IP, which wasn’t always the case.)