Final answer:
The most important physical feature in the Rocky Mountain region is the Rocky Mountains themselves, which were formed during the Laramide Orogeny. They are no longer growing but have been glaciated and eroded over time.
Step-by-step explanation:
The most important physical feature in the Rocky Mountain region is the Rocky Mountains themselves. The Rocky Mountains stretch from New Mexico to Northern Canada and were formed around 80 to 55 million years ago. They are the result of a large-scale deformational event called the Laramide Orogeny, which caused mountain building. The Rocky Mountains are no longer growing but have been glaciated and eroded over time.