How many US states west of the Mississippi River lie on the Canadian border?

Of the thirteen U.S. states that share a border with Canada, five are located entirely west of the Mississippi River. These states, from east to west, are North Dakota, Montana, Idaho, Washington, and the non-contiguous state of Alaska. Together, their borders with Canada stretch for thousands of miles, traversing diverse and often remote landscapes. This international boundary is the longest in the world between any two countries.

The border's path west of the Mississippi is a product of historical treaties and geographical features. For instance, much of the border along North Dakota and Montana follows the 49th parallel, a line of latitude established by the Treaty of 1818 between the U.S. and Great Britain. This straight line cuts across prairies and the Rocky Mountains. In contrast, the borders of Idaho and Washington with British Columbia are defined by mountainous terrain and river systems.

Alaska's border with Canada is the longest, stretching for 1,538 miles. This vast and largely wild frontier is defined by the 141st meridian west and the rugged peaks of the St. Elias Mountains. Across these five states, numerous border crossings serve as vital links for trade and tourism, connecting communities and economies. From the plains of North Dakota to the forested mountains of the Pacific Northwest and the remote wilderness of Alaska, these five states represent the western extent of the peaceful and historic relationship between the United States and Canada.