Article from November 1977 issue of The Dakota Sun Newspaper. The newspaper was published by Standing Rock College (now Sitting Bull College) from the 1977 to 1985. Sitting Bull College Library has physical copies as well as a microfilm edition. A guide to the microfilm edition is available here
Although Bigfoot sightings are reported from time to time and anecdotal stories of encounters are common, Bigfoot is most famous on Standing Rock for a spate of 28 sightings from 1977 that took place mostly around Little Eagle, South Dakota. Believe what you will about the Bigfoot, what is indisputable is that the creature caused a stir on Standing Rock in the 1970s.
I have heard that video was made during that time by National Geographic or the then famous Mutual of Omaha's Wild Kingdom, but have been unable to verify either. It would be great to find any such documentary that might have been created at that time and have a copy at the library.
The most complete recounting of the events can be found in a 1978 Minnesota Archaeologist article titled "Contemporary Stories of Taku He or Bigfoot in South Dakota as Drawn from Newspaper Accounts" by Mark Hall. A copy can be read at the library. A basic description of each of the sightings drawn from the article can be read here, while the article contains more complete descriptions.
Several books detail the events in more succinct form, one of the best of which is NDSU's Professor Tom Isern, who recounts the events and his 80s visit to Little Eagle in the book "Plains Folk II: The Romance of the Landscape".