Answer:
To give historical background on the Kiowa route to Rainy Mountain.
Step-by-step explanation:
N. Scott Momaday's "The Way to Rainy Mountain" is a sort of folklore infused memoir telling the history of the Kiowa people. The story details the journey of the writer's ancestors from their home in Montana to the Rainy Mountains in Oklahoma.
The prologue acts as the introduction of the book. In it, he details the historical background of the Rainy Mountain, how it came to be named and how the Kiowa tribe had come to this place. The introduction provides an insight into the physical setting of the Rainy Mountain.