ghats!
The mountain range that forms a border with Spain and France is the Pyrenees Mountains. The border that separates the two counties runs at the highest point of the Pyrenees' Mountain Range.
The Appalachian Mountains formed the western border to the eastern colonies in North America.
The Tatras.
Andes
The Rocky Mountain range in Alberta runs along the lower half of the western Alberta border.
The Rocky Mountains formed the western border of the Louisiana Purchase.
The Pyrenees mountain range forms a natural border between the Carolingian Empire and Spain.
The rockies
Elburz Mountains
The Sierra Nevada mountain chain.The Sierra Nevada Mountain Range.
The Carpathian Mountains.
The Pyrénées are straddling the border with Spain in south-western France, the Alps separate France from north-western Italy and the Jura mountain range is located on the Switzerland border.