* Appalachian Mountains: Located in the eastern part of North America, they mark the southeastern boundary of the Canadian Shield.
* Rocky Mountains: Located in western North America, they mark the western boundary of the Canadian Shield.
It's important to note that the boundary isn't a clean, straight line. The Canadian Shield is a vast, ancient geological formation, and its edges are often marked by transitions rather than abrupt changes. The Appalachian and Rocky Mountains represent the most prominent and visible boundaries of the Shield.
