Laos!
The Uruguay River forms the western border of Uraguay with Argentina.
The Mississippi River forms the western border of Illinois.
The Mississippi river forms the western border of the southern colonies.
The Uruguay River forms the western border of Uraguay with Argentina.
Minnesota only forms a border for one country: Canada.
The western border of Moldova is formed by the Prut river.
The Mississippi River forms the western border of Illinois.
Mississippi is the state named after the Mississippi River that forms most of its western border.
California's eastern border and Arizona's western border.
The Mississippi River forms the wavy western border of Illinois. And the Ohio Wabash River is the southern border of Illinois.
Pacific Ocean