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Canada–United States border
Longest international land border
The boundary between Canada and the United States runs 8,891 km, including the stretch between Alaska and Canada. It is the longest border between two countries.
The International Boundary Commission, a joint Canadian-American body, maintains the line and reports its length as 8,891 km, including the Alaska-Canada section, about 2,475 km of which is generally cited for Alaska. The commission was established by the 1908 Treaty and made permanent by a 1925 treaty.
The boundary is marked on the ground by more than 8,000 monuments and reference points, and a cleared strip about 6 m wide (3 m on each side) called the vista is kept free of trees and brush where the line crosses forest. The commission also maintains hundreds of official maps and over a thousand survey control stations.
Most of the boundary had been surveyed by 1874, but monuments were lost and the line became overgrown by 1908, which is why it had to be re-established. Slightly different totals appear in other sources, such as 8,893 km, because of survey methods and rounding; the two countries' own figure is treated as the authoritative one here.
The border is crossed at hundreds of ports of entry, and a few places, such as the town of Derby Line, Vermont and Stanstead, Quebec, straddle it closely.