Most of the northern boundary is formed by the Alps. However, on the Iberian Peninsula, the Pyrenees form another northern border of Southern Europe.
ALBORZ
Elburz Mountains
Himalayas
The 49th Parallel.
The Carpathian Mountains.
West Virginia, Ohio, Illinois, and Indiana form the northern border of Kentucky, along the Ohio River.
The 42nd parallel forms the southern boundary of Idaho. It marks the border between Idaho and Nevada as well as a portion of the border between Idaho and Oregon.
Rio Grande forms the Southern border of the United states.
Rio Grande forms the Southern border of the United states.
Rio Grande makes up most of the southern border of the United States, it also makes up most of the northern border of Mexico
Kentucky forms most of the northern border of Tennessee.