These monuments are patterns of significant events made of stones by the aboriginal people who once lived here. Some of the monuments are of humans, others animal figures. These effigies represent personal or tribal tragedies; others represent the resting-place of a tribal leader.

One of the monuments in the Big Muddy is the Turtle Effigy. The head of the turtle faces southeast towards a human effigy. The turtle has a face, ears, legs and a tail. In the center of the turtle there are Chokecherries growing. In Dakota Black Foot legend, turtles represented a wise and highly respected person.