The two rivers that partially form the eastern boundary of the United States are the Mississippi River and the St. Lawrence River. The Mississippi River flows southward from Minnesota to the Gulf of Mexico, serving as a significant boundary for several states. The St. Lawrence River, situated in the northeastern part of the country, forms part of the boundary between the United States and Canada.
mississippi river
The Saint Croix and Mississippi Rivers form part of the boundary between Wisconsin and Minnesota.
Mississippi
Missouri River BasinThe Missouri River starts in Montana and flows through North and South Dakota, forms the boundary between Nebraska and Iowa and part of the boundary between Kansas and Missouri, and flows through Missouri to the Mississippi River.
The Mississippi River and its tributaries drain all or part of 31 states and a small part of one Canadian province.
The river that separates the east and west U.S. is usually considered the Mississippi.
Utah
The Colorado River forms part of the southwest boundary of the United States.
The Louisiana Purchase expanded the southern part of the United States. It included many future states, but did not include the upper part of the Mississippi River.
The Rio Grande River
Indiana and Illinois