Final answer:
The Rocky Mountains formed the western boundary of the Plains Native American cultural region. This area, extending from Texas to Canada and from the Mississippi to the Rockies, was inhabited by nomadic tribes adapted to the plains environment.
Step-by-step explanation:
The geographic feature that formed the western boundary of the Plains Native American cultural region is the Rocky Mountains. This region, which includes a wide expanse of flat land and rolling hills, lies to the east of the Rocky Mountains. The Plains tribes lived in an area that extended from what is now Texas in the south to Canada in the north and stretched from the Mississippi River in the east to the Rocky Mountains in the west.
The nomadic Plains tribes, such as the Comanche and Sioux, adapted to the relatively sparse environment of the Plains. They had a unique culture based on buffalo hunting and were known for their tepees and horse-riding skills. Other tribes were involved in agriculture, growing crops such as corn and squash.
The Rocky Mountains serve as a geographical divide, providing a distinct western boundary to the Plains Native American cultural region. The tribes living to the west of the Rockies, in contrast, had a different culture and lifestyle, adapted to a more mountainous and forested environment.
Learn more about Plains Native American cultural region