The Saint Lawrence forms part of the eastern border between the United States and Canada. Other rivers that form the border include Rainy River, Pigeon River, and Niagara River.
please be more specific, the U S and what other country/ Mexico or Canada. or do you mean between states?
st.lawrence
New Brunswick, Canada is east of Maine, USA.
The Snake River forms part of Oregon's eastern border
The Mississippi River forms most of Arkansas's eastern border.
Lake Amur
Rio Grande forms the Southern border of the United states.
The 49th parallel of latitude forms the border between Canada and the US from Lake of the Woods to the Georgia Strait. The 45th parallel of latitude also forms part of the border between Canada and the US along the northern boundaries of the states of New York, Vermont and New Hampshire.
The Black Sea forms a small portion of the Eastern border of Europe. The Mediterranean is also part of the Southeastern border.
The Atlantic Ocean forms the eastern and southern border of New England.
Eastern Border
The Colorado River forms the border between California and Arizona.
The 49th parallel
Great Lakes