UFO sightings in South Dakota
The 1953 Ellsworth Air Force Base case near Rapid City, a radar-visual event tracked by ground and airborne radar and seen by observers, was left 'unidentified' by Project Blue Book and remains one of its stronger unknowns.
Saw something over South Dakota?
Most strange lights have an ordinary cause. Run the identifier: seven questions and the three most likely explanations, from a Starlink train to Venus to a drone, each with how to confirm it.
Note the exact time, the compass direction, the height above the horizon, how long it lasted and how it moved. Check a flight tracker and a satellite app before deciding it is unexplained.
File it. The National UFO Reporting Center and MUFON take reports from every US state, South Dakota included, and their databases are where the per-state counts actually live.
Other states with famous cases
The famous cases above follow the public record; XenoAtlas documents claims and their explanations and takes no position on whether any involved non-human contact. Per-state sighting counts are maintained by NUFORC and MUFON. For the big cases on a map, see the case files.