This Bell System diagram shows the layout of the permanent and recurring
broadcast line connections on the West Coast, as of January 15, 1929. This clearly
indicates why NBC first placed its West Coast network headquarters in San Francisco.
Similar diagrams from 1938 show that new lines had been installed for all networks,
running from Salt Lake City directly to Los Angeles. That year marked the beginning of
an exodus that saw virtually all West Coast network program origination move to
Los Angeles within a few years.