I know that K preceeds the three call letters west of the Mississippi and W preceeds the three call letters east of the river. I've visited a couple of stations in order to pick up a few prizes. But that's about it.
1) When would FM stations really start to come into the air waves?
2a) At this time, or at what time, did stations start to take call in requests and the like?
2b) What would the procedure be at this time for taking calls at the station?
3) Also in this time frame, would stations be general hit music stations or might there be more specific stations?