The country that forms the eastern boundary of Niger is Chad. Niger shares a border with Chad that is approximately 1,175 kilometers long, running along the southern edge of Chad's Lake Chad region. This border plays a significant role in the geography and regional dynamics of both countries.
Spain forms the eastern boundary of Portugal.
Spain is the only country to border Portugal to the east.
The country is Eritrea, and it's eastern boundary is formed by the Red Sea.
The Indian Ocean forms the eastern boundary of Africa.
The southern half of the eastern boundary of Alabama is the Chattahoochee River.
the country that forms the northern boundary of the United States is Canada :)
The Atlanic Ocean
Minnesota.
Mississippi
The Connecticut River
Mississippi
The Mississippi River is the East boundary for Arkansas.