Unfortunately, the great opportunity that came in the form of that amazing title might end up being wasted on this article, seeing as the details on this event are very scant. It was 1934, and a farmer local to the area around Lake Campbell in eastern South Dakota was plagued with a spate of missing livestock. Whatever he thought might've been to blame for these disappearances, I can't imagine that he thought it very likely that it was the work of a creature seemingly ripped from the frames of Jurassic Park - and yet that is exactly what presented itself to him on one fateful occasion.
South Dakota Saurian[]
This great illustration of this obscure case comes from Trendorman on DeviantArt.
The farmer's tractor gently chugged along a road near to Lake Campbell, and I can imagine that the farmer driving it might've been whistling a peaceful tune. However, this would all change when an enormous, four-legged reptile suddenly strolled onto the road, leading the panicked farmer to swerve his vehicle off the road and into a nearby ditch in an effort to avoid the colossal critter. Just as quickly as it had arrived, the monster vanished off towards the lake in question.
Bewildered, the farmer brought some help with him when he next returned to the scene of the reptilian manifestation. This group of makeshift monster-hunters discovered a trail of unidentifiable footprints that seemingly came from a large, four-legged animal. The footprints moved through a nearby muddy field and then toward Lake Campbell. Sadly, this where the story ends in all the sources I have been able to find.
Is This Story Extinct?[]
So this is a tiny nugget of an interesting story, but it is reported on both Mysterious Universe and in 'Visitors from the Twilight Zone' by David Pratt - and there are more details in the MU article than there are in Pratt's brief reference to the case, implying that there must've been some other source from which the writers of Mysterious Universe found their information, which I haven't yet been able to locate. A cryptozoology buff that I briefly talked to online pointed out that there is a possibility that this story was actually a publicity stunt for the nearby Wall Drug - which has a famous mechanical Tyrannosaurus head as part of its decoration. I am not certain about this specific theory, but I'm leaning on the side of thinking that this story was likely naught more than a newspaper hoax. An interesting one, yes, but a newspaper hoax nonetheless.