I know that after the 10 p.m. news on WWOR-TV, the superstation feed replaced the syndicated fare with reruns of Magnum P.I.
KTVU was available on PrimeStar satellite, channel 120.But what about Superstations like KTVU Oakland
Content or lack of original programing. The big 3 now 4 OTA networks spent big bucks developing programing. They also made serious money off of having local affiliates. Plus their OTA signals reached folks not on cable which made sponsors happy. Satellite dishes were relatively expensive and not the most attractive yard decoration. My HOA allows them only if not seen from the street. Also local affiliates help in news gathering. I believe the ABC, NBC, and CBS still make money on their half hour evening newscasts,And why weren't any popular enough to join or replace the Big Three?
I think you mean KMSP and not KSTP (KSTP is the ABC and was the NBC before that). KMSP Minneapolis (Fox) was the independent for years before they were Fox and UPN and was shown in the Dakotas, Minnesota and Western Wisconsin (and assume northern Iowa)I would assume most strong independent, like KPLR, WTTV, KSTP (and WTCN before it), WCIX all got decent regional carriage in markets nearby which had no independent.
And wrestling from Fort Worth's Will Rogers Coliseum on Saturday nights. I lived in southeastern Arkansas in the late '70s/early '80s and our cable system had KTVT and another DFW station, KXTX, a CBN (Pat Robertson's outfit) affiliate. I wonder what KXTX's reach was compared to KTVT.KTVT was a major superstation in the South during the '80s and early '90s. Excellent movie selection, sports, top-rated cartoons, and syndicated repeats.

I did mean KMSP, thanks for the catch. I recall going up to our relatives in Northern Minnesota, places like Hibbing and Int'l Falls and they had WTCN and some Winnipeg station as well. WTCN well covered Minnesota for cable before it became an NBC station.I think you mean KMSP and not KSTP (KSTP is the ABC and was the NBC before that). KMSP Minneapolis (Fox) was the independent for years before they were Fox and UPN and was shown in the Dakotas, Minnesota and Western Wisconsin (and assume northern Iowa)
From what I could tell, Manistee, MI had WTBS and WGN only. Both were on cable by 1980, with WTBS being added in 1977 (when it was still WTCG). Oddly, WKBD was never carried there, but WVTV from Milwaukee was apparently carried in the early days. The first few years of FOX went unseen AFAIK until local affiliate WGKI signed on in 1989. WWOR was rare in Michigan from what I could tell.
Speaking of WGKI, it was seen in most of the Upper Peninsula and into northern Wisconsin between 1995 (WKBD dropping FOX) and 2003 (the UP getting its own FOX affiliate).
I remember Grand Rapids having WKBD until around 1999, when a local UPN affiliate signed on and picked up most if not all of WKBD's sports rights at the time. I'm too young to remember if Grand Rapids dropped WKBD at some point in the early 90s before bringing it back when it picked up UPN (Grand Rapids didn't have its own UPN affiliate until 1999 and never had a primary WB affiliate; the local PAX station carried WB programming on a one-day delay after WGN Superstation (which had universal cable carriage in West Michigan) dropped WB shows)
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Windsor is the Canadian city closest to Detroit.I believe that Canadian cable companies carry the US network stations. The stations vary by region. I think Ottawa gets the Detroit stations. Could be wrong as there are US TV markets closer to Ottawa, but Detroit is the only major market on the border in the Eastern Time Zone.