A hoodoo is a rock formation caused by differential erosion, i.e., parts of it are harder/softer than other parts, thus causing the softer parts to erode more quickly. In the Milk River Valley, sandstone hoodoos predominate, having been exposed for 15,000 years or more since the last ice age.

The Blackfeet believed that the Milk River hoodoos were home to powerful spirits. Plentiful game and berries ensured that this area was a seasonal migration stop for both the Blackfeet and Shoshone, as well as perhaps others.