WMBD stands for World's Most Beautiful Drive, which is what president Theodore Roosevelt
proclaimed Grand View Drive in Peoria, Illinois
is. At the time, it may well have been as I doubt there were too many roads that could be driven during his presidency. By now I'm sure that more beautiful drives exist.
Besides being the call letters for the Peoria CBS TV affiliate, WMBD are also the call letters for 1470 on the AM radio dial.