The facility encloses a prehistoric sinkhole that formed and was slowly filled with sediments during the Pleistocene era.

[1][2][3] During the Late Pleistocene, the sinkhole at Mammoth Site of Hot Springs formed when a cavern in the Minnelusa Limestone collapsed.

Because of the steep sides of very slippery Spearfish Shale, mammoths were occasionally trapped as they were unable to find a foothold and climb out of the sinkhole during periods of low water.

Over thousands of years, the "hardened mud plug" inside the dried-up pond has remained stable.

Findings at the site include the remains of megafauna such as giant short-faced bears along with those of shrub oxen, American camel, llama, wolves, coyotes, birds, minks, ferrets, prairie dogs, voles, and moles.

Initially, several attempts were made to radiocarbon date collagen from scrap mammoth bone recovered from the site.

The results of the TL dating were apparently never published and preliminary OSL ages indicate that the sinkhole and its associated sediments and mammoth bones are indeed older than 26 ka.

[1][3] In 1974, a construction worker, George Hanson, unearthed unusual bones while the area was being prepared for a new subdivision.

[4] Phil Anderson agreed to donate the entire bone bed and mineral rights to the nonprofit organization and along with the work performed by amateur and professional excavators, led to its status as a museum, and it was designated a National Natural Landmark in 1980.

[13] The museum's visiting scientists have included specialists from Mexico, Italy, Netherlands, Great Britain, Russia, and Germany.