Which State Has the Longer Border with Canada: North Dakota or Idaho?

North Dakota shares a significantly longer border with Canada than Idaho.

• North Dakota: Approximately 499 miles (803 km) of land boundary with the Canadian provinces of Saskatchewan and Manitoba.
• Idaho: Only about 45 miles (72 km) of border with British Columbia, at the state’s northern tip.

The difference stems from geography: North Dakota’s entire northern edge runs along the 49th parallel, while Idaho’s Canadian boundary is a short segment at the top of its panhandle.