The Atlanic Ocean
Spain forms the eastern boundary of Portugal.
Georgia's eastern border is the Atlantic Ocean
The Indian Ocean forms the eastern boundary of Africa.
The southern half of the eastern boundary of Alabama is the Chattahoochee River.
Spain is the only country to border Portugal to the east.
Minnesota.
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.