Here's a breakdown:
* The Rocky Mountains stretch from Canada down through the western United States.
* The Appalachian Mountains run along the eastern edge of North America, from Canada to Alabama.
* The Great Plains extend from the foothills of the Rockies to the Mississippi River.
* The Canadian Shield is a vast, ancient, and rocky expanse that covers much of eastern and central Canada.
* The Mississippi River flows from its headwaters in Minnesota all the way south to the Gulf of Mexico.
While there are some exceptions (like the Great Lakes, which are more east-west), the dominant trend is for the major landforms to run north-south. This is due to the tectonic forces that shaped the continent over millions of years.
