Spain forms the eastern boundary of Portugal.
The river that forms part of Alabama's eastern border is the Chattahoochee River. It flows southward and serves as a natural boundary between Alabama and Georgia. The river is significant for both its ecological importance and its role in regional water supply.
The Indian Ocean forms the eastern boundary of Africa.
Spain is the only country to border Portugal to the east.
Minnesota.
The Atlanic Ocean
Mississippi
The Connecticut River
Mississippi
The Mississippi River is the East boundary for Arkansas.
The country is Eritrea, and it's eastern boundary is formed by the Red Sea.
Two rivers partially form Illinois State's Eastern boundary. The Wabash River is one river that forms Illinois' boundary. The Ohio River is the other river that forms the state's boundary.