Alaska shares the longest land border with Canada of any U.S. state.
Its boundary with Canada runs for about 2,475 kilometres (1,538 miles), mainly alongside Canada’s Yukon territory and British Columbia. Alaska’s southeastern panhandle reaches toward the Pacific, while its eastern and northeastern edges meet Canadian territory.
The commonly confused answer is Montana, which ranks highly among the contiguous states but has a shorter Canadian border—about 877 kilometres. Michigan, Maine and Minnesota also have substantial boundaries with Canada, including stretches running through lakes and waterways.
Alaska’s Canadian border was shaped after the United States purchased Alaska from Russia in 1867. Later surveys and agreements settled much of the boundary, including the Alaska–Yukon and Alaska–British Columbia sections. Alaska is therefore not only the largest U.S. state by area but also the state with the longest Canadian land boundary.