What mountain range forms the natural border between the United States and Canada?

The Rocky Mountains are the mountain range that forms the natural border between the United States and Canada. This extensive range stretches from northern New Mexico all the way to Canada, making it a significant geographical feature in North America. The Rocky Mountains serve as a natural divider, with the eastern slopes primarily in the US and the western slopes extending into Canada. The presence of multiple national parks and breathtaking scenery within this range further emphasizes its importance as a landmark between the two countries.

In contrast, the Appalachian Mountains are located on the eastern side of the United States and do not extend into Canada. The Sierra Nevada Mountains are situated entirely in California and do not share a border with Canada. The Cascade Mountains, found in the Pacific Northwest, predominantly run through Washington and Oregon, again lacking a connection with the US-Canada border. Thus, the Rocky Mountains stand out as the defining natural boundary between the two nations.