How many states border Canada?

Thirteen U.S. states share a border with Canada, including the contiguous border states from east to west: Maine, New Hampshire, Vermont, New York, Pennsylvania, Ohio, Michigan, Minnesota, North Dakota, Montana, Idaho, and Washington, plus Alaska, which shares about 1,538 miles of border with the Canadian provinces of Yukon and British Columbia. Alaska's border is by far the longest segment. The total U.S.-Canada border, including the Alaska section, is about 5,525 miles, the longest international border in the world between two countries. The contiguous portion of the border (excluding Alaska) is about 3,987 miles.

The border generally follows three categories of features. From east to west across the contiguous United States: a roughly straight surveyed line and several rivers from northern Maine across New Hampshire and Vermont; the St. Lawrence River and the Great Lakes (Ontario, Erie, Huron, and Superior) from northern New York through Michigan to Minnesota; surveyed lines and Lake of the Woods through Minnesota; and the 49th parallel of north latitude from Lake of the Woods west to the Strait of Georgia in Washington. Pennsylvania and Ohio border Canada only across Lake Erie. Pennsylvania's Erie shoreline measures about 51 miles, the shortest Canadian frontier of any of the 13 border states.

The complete list of the 13 border states is sometimes a tricky civics question because many people forget Pennsylvania (whose Lake Erie shoreline does not extend far) or Ohio (which similarly borders Canada only across Lake Erie). The Alaska-Canada border is the longest segment, established by the Alaska Treaty of 1867 (which transferred Russian Alaska to the United States) and refined by various surveys and the Hay-Herbert Treaty of 1903 settling the Alaska-Canada boundary dispute. The border crosses through some of the most remote and rugged terrain in North America, including the Coast Mountains, the Saint Elias Mountains, and the Yukon River valley.

The U.S.-Canada border is mostly demilitarized, with no permanent military installations on either side, although both countries maintain border patrol agencies (U.S. Customs and Border Protection and the Canada Border Services Agency). The International Boundary Commission, established by the 1908 treaty between the U.S. and Britain (acting for Canada), maintains the border markers and visibility through forest cuts. The two countries share the Treaty of Boundary Waters of 1909 governing water rights and the International Joint Commission for managing shared rivers and lakes. Crossing points along the border include the Peace Bridge (Buffalo-Fort Erie), the Ambassador Bridge (Detroit-Windsor), and the Peace Arch (Blaine, Washington-Surrey, British Columbia).