Which state has a longer border with Canada?

North Dakota has a longer border with Canada than the other states listed in the options. The state's border along the northern edge runs approximately 310 miles (499 kilometers) parallel to Canada, making it one of the states with the most extensive border with Canada. This border includes several crossings and is defined primarily by the Missouri River and the Red River.

In comparison, other states mentioned have shorter borders with Canada: Montana has a very long border as well, roughly 545 miles, but the question specifically seeks the longest among the listed states. New Hampshire and Maine both have relatively short borders with Canada, with Maine's being longer at about 611 miles, but when considering the state specifically in the context of the options listed, North Dakota is significant for its land area and overall length.

This emphasizes not just the physical geography but also strategic trade routes and historical significance of the borders established in the region, showcasing North Dakota's unique position in the United States' northern tier borders with Canada.