The Bell System history tells that they recognized the traffic of big cities would not fit on Step-by-Step switching because of the switch's limited decimal choices. Panel switching was developed to give more flexibility and choices in city service.
However, Los Angeles remained Step by step because the Bell System inherited existing exchanges. The history says despite things like graded multiples network mgmt in LA proved difficult, but they did not elaborate.
I know Bell Labs developed SxS add-ons in the 1960s and 1970s to improve SxS functionality, but that was much later. An early short haul toll itemized message accounting system was developed for LA.
As Los Angeles turned into a big city (1950s?), how did the Bell System handle inter-exchange traffic within the limits of an SxS switch? Did they rely on tandems? Did they have to overtrunk at high expense? Did they put in No 5 Crossbar when it came out?
Thanks.
[public replies, please]