The Rocky Mountains are the largest mountain range of North America. They range almost from Mexico to Alaska. They are the big dividing element between the east and the west. The continental divide runs through the rockies, and many animal and plant species are found either only west of the Rocky Mountains or only east of them.
But the Rockies are not only a high mountain range. They contain many valleys and high plains. For example, the Yellowstone National Park lies in the middle of the Rockies, one of the gems of the National Parks of the USA.