We learn the answer to these questions in the first two paragraphs of the introduction.

According to Momaday, Rainy Mountain is located in Oklahoma, to the northwest of the Wichita Range. It is a site of remarkable significance for the Kiowa people, and for Momaday, it represents a significant link with his family’s past. Rainy Mountain is described as a “single knoll” which may make it sound insignificant. To the Kiowa people, however, it is a landmark with spiritual significance. The Wichita Mountains are very old in geological terms, which is arguably representative of the ancient meaning that Rainy Mountain has for Momaday and the Kiowa people.

The reason for his return is a desire to honor his Kiowa heritage as well as to be at the grave of his grandmother, who died a few months prior. There were a number of reasons that he felt the need to make this trip, all linked to his need to reconnect with his people, despite the facts that he does not speak the language of his people and that his understanding of his cultural origins is tenuous at best. In fact, it had been his grandmother who had told him just about everything he knew about his culture, adding an extra layer of significance to his journey to her gravesite.

Rainy Mountain is a geographical feature that stands apart from the Wichita Mountains in the state of Oklahoma. This unusual part of the natural landscape has considerable cultural, religious, and historical significance for the Kiowa people, of which Momaday is a part.

Once upon a time, it was a symbol of home for the Kiowa, a place where they could live in peace and relative safety, just as their ancestors had done for generations. But this all changed when the Kiowa, like so many Native American tribes, were defeated by US military forces and driven from their land.

Despite this massive setback and the inevitable decline of Kiowa culture that followed, Rainy Mountain still retains a very special place in the hearts of all members of the tribe. It stands as a living symbol of what once was, of a proud and ancient culture that had thrived undisturbed for centuries before the arrival of the white man on American soil.

The immediate catalyst for Momaday's return to Rainy Mountain is the recent death of his grandmother Aho; he wants to visit her grave. However, there's also something deeply symbolic about Momaday's return. In coming back to Rainy Mountain, he's reestablishing a connection with his tribal heritage and, in the process, playing his part in keeping Kiowa history and culture alive.

In the prologue, we learn the reason why Momaday returns to Rainy Mountain:

Scott Momaday describes the location of Rainy Mountain quite precisely in his book The Way to Rainy Mountain. He says that:

A single knoll rises out of the plain in Oklahoma, north and west of the Wichita Range. For my people, the Kiowas, it is an old landmark, and they gave it the name Rainy Mountain.

The Wichita mountain range is a mountain range located in southwestern Oklahoma. It consists of igneous rocks that were uplifted 330 to 290 million years ago and have since gradually been worn down by erosion. The peaks average approximately 2,000 feet above sea level. Rainy Mountain is slightly to the northwest of the rest of the range. It is located in Kiowa County, Oklahoma, and served as a landmark and spiritually significant site for the Kiowa people. 

The narrator returns to the mountain to visit the grave of his grandmother after her death. It is part of his physical and spiritual journey to reconnect with his people and their origins. 

Rainy Mountain is located northwest of the Witchita range in Kiowa County, Oklahoma. The narrator returns there to visit his grandmother's grave.

Rainy Mountain was a landmark for the Kiowa people, from whom the narrator is descended. He says that it had some of the harshest weather in the world, including blizzards and heat. Momaday says the Kiowa are people who prefer the summer and deal with the winter. 

Momaday has a lot of love for his grandmother, who died after a long life. After his grandmother dies, Momaday first goes to her house where there is nothing but quiet. The next day, he goes to Rainy Mountain to see her grave. He writes:

The next morning I awoke at dawn and went out on the dirt road to Rainy Mountain. It was already hot, and the grasshoppers began to fill the air. Still, it was early in the morning, and the birds sang out of the shadows. The long yellow grass on the mountain shone in the bright light, and a scissortail hied above the land. There, where it ought to be, at the end of a long and legendary way, was my grandmother's grave. Here and there on the dark stones were ancestral names. Looking back once, I saw the mountain and came away.

To view Rainy Mountain's location, click on the Google Maps reference link.

Momaday tells us this in the first two paragraphs of his Introduction. Rainy Mountain is a special place to the Kiowa people, the author’s Native American ancestors. It is a rounded hill that stands alone but near the Wichita Mountains in southwestern Oklahoma. Below is a link to the nearby national wildlife refuge. Rainy Mountain is not part of this protected land; yet looking at the photographs on this site will give you an idea of the terrain.

The author goes back to Rainy Mountain one July, after his grandmother has passed away. She was his last living link to the traditional ways of the Kiowa. He wanted to honor and remember her as well as the many others who had gone on before. The cemetery is located near the mountain. Momaday’s return was part of his longer personal journey of tracing the historic migration of the Kiowa from the headwaters of the Yellowstone River in western Wyoming and Montana, east and south through the Black Hills and plains to Oklahoma.