Darn, I missed it... [b]Yesterday[/b] was the 70th anniversary of the Big Shift of 1941.
The vast majority of North American radio stations changed frequency, usually in blocks.
540-730: no change
A few examples:
WTMJ-620, Milwaukee: no change
WSB-750, Atlanta: moved from 740
WLS-890, Chicago: moved from 870 (and took along timesharing partner WENR)
WHA-970, Madison: moved from 940
WBZ-1030, Boston: moved from 990 (and took along "booster" WBZA, Springfield)
KNX-1070, Los Angeles: moved from 1050
WPHT-1210, Philadelphia: moved from 1170 (and was known at the time as WCAU)
WCLO-1230, Janesville: moved from 1200
KGA-1510, Spokane: moved from 1470
WDAN-1490, Danville: moved from 1500
A few stations, especially in Canada & Mexico, moved "out of pattern".