Here are a couple more interesting historical maps from Bell, specifically from The Bell System Technical Journal in 1930.

The first shows "special contract telegraph circuits furnished to a brokerage company" (30 circuits / 95 stations / 38K km): http://i.imgur.com/vL4W8Vz.jpg

The second shows "special contract telegraph service furnished a press association" (53 circuits / 124K km) : http://i.imgur.com/ZEsBKKe.jpg

Lots more fun maps and diagrams @ https://archive.org/stream/bellvol9systemtechni00amerrich/be...