Because that is how it was formed there is more mountains there.
Western North America is more mountainous.
The western side of North America is more mountainous.
western North America
Western North America is more mountainous.
western
Western.
EAstern :)
Although both sides are both mountainous, the western side of the US has a much more mountainous landscape. But it is mostly the Northern Butte side.
The western part of North America since it is where the Rocky Mountains are.
Western North America is more mountainous.
Western because the Rocky Mountains
The more mountainous is the western side of north America