Rio Grande forms the Southern border of the United states.
No one state forms the "most" northern border. "Most" implies the majority of something, or more than half. Michigan has the longest border with Canada of the Contiguous US: 720 miles or about 19% of the Contiguous US border with Canada.
Keep in mind that this border with Canada is not 100% Michigan's northern border. If one travels due south from Detroit, they end up in Canada before they would get to Ohio.
For reference, Alaska has a 1500+ mile eastern border with Canada.
Maine (611 miles), Minnesota (547 miles) and Montana (545 Miles) round out the top 5 in length of Canadian border.
Canada is the northern border for the upper 48 states.
Canada forms most of the northern border of the United States.
Canada forms most of the northern border of USA.
Canada forms the entire northern border of the "lower 48" states either through land or water.
Canada forms most of the northern border of USA.
Canada
Canada.
Canada.
The country that forms most of the northern border of the United States is Canada. The country directly to the south is Mexico.
The country that forms most of the northern border of the United States is Canada. The country directly to the south is Mexico.
Canada
Canada
Canada
The largest country in the world: Canada
Canada is.
Canada
Canada forms the most northerly border of the U.S.
Canada forms the northern boundary of the United States.
Canada
The US. :)