In the early 1960s, WROC-TV in Rochester, NY (then on Channel Five, later on Channel Eight) pre-empted most of the NBC prime time schedule on Monday nights. Starting in the winter of 1961 they ran their own movie series, called "Featurama", highlighting postwar movies in color. During the 1960-61 season that meant Rochester didn't see Riverboat, Tales of Wells Fargo, Dante, Barbara Stanwyck and Milton Berle's Jackpot Bowling that season--none of them big hits against The Rifleman, Red Skelton or Garry Moore (which aired on the city's CBS/ABC affiliate) nationally. The pre-emption continued through the summer of 1962, although the movie start shifted from 8 to 9 PM, which meant Rochester did see the prime time airing of The Price is Right, though 87th Precinct and Boris Karloff's Thriller got time-shifted to another night.
That all ended in the fall of 1962 when a third VHF full power station came on the air in the market as a fulltime ABC affiliate (and could even have stolen the NBC franchise if WROC hadn't changed hands and the new locally based owners promised to cut down on the pre-emptions). Stations could spike network shows back then if they thought they'd make more $$ or deliver better numbers by pre-empting a weak night on the net with a local show that would bring in local ad accounts' cash. It was only when new competition in a market weakened stations' positions in the early 60s that the pre-emptions in upstate NY became less frequent.