How does the Canada-US border length compare to other international borders?
Executive summary
The Canada–United States international boundary is commonly reported as the longest in the world at about 8,891 kilometres (5,525 miles), a figure maintained by the International Boundary Commission and reflected in multiple summaries [1] [2]. That total combines a 6,416 km stretch between Canada and the contiguous U.S. and a separate 2,475 km Alaska–Canada section, which together outstrip other bilateral land borders though measurement methods and definitions produce some differing totals in the public record [2] [1] [3].
1. The raw numbers and why they vary
Authoritative sources list the full Canada–U.S. boundary at roughly 8,891 km (5,525 mi) as shown on the International Boundary Commission’s official maps [1], while encyclopedic and government summaries repeat that total and break it into a 6,416 km contiguous section and a 2,475 km Alaska section [2]. U.S. government technical reports cite the contiguous U.S. line alone at about 3,987 miles (≈6,416 km) and the Alaska line at about 1,538 miles (≈2,475 km), yielding the same combined magnitude but highlighting the choice to report either component or the whole depending on context [3] [4]. Other organizations and secondary sites sometimes quote slightly different figures — for example one private boundary site lists 6,435 km for a particular land-only measure [5] — underscoring that coastline definitions, inclusion of waterways, and mapping scale change totals [4].
2. How it compares to other international borders
Measured end‑to‑end, the Canada–U.S. boundary is treated as the world’s longest international land border, a claim repeated in statistical compilations and public reporting [6] [2]. The single contiguous section between Canada and the lower forty‑eight U.S. states is often described as the second‑longest continuous border after the Russia–Kazakhstan stretch when that specific comparison is made, but when the Alaska segment is included the Canada–U.S. pairing becomes the longest total bilateral border [2]. By contrast, the U.S.–Mexico border is roughly 1,933 miles (≈3,112 km), far shorter than either component of the northern boundary or its sum [3] [7].
3. Measurement caveats that change the narrative
Border length is not a single objective number: different authorities use different map scales, include or exclude water boundaries and Great Lakes shorelines, or count “coastline effects” that can multiply apparent lengths; the Congressional Research Service notes alternate charting methods can more than double or massively increase measures when smaller chart scales are used [4]. Databases and commercial aggregators may therefore amplify or truncate the Canada–U.S. total to fit a headline — “longest in the world” — while technically defensible alternate numbers exist depending on inclusion rules [6] [5] [4].
4. Why the distinction matters beyond trivia
Framing the Canada–U.S. boundary as the world’s longest serves policy and cultural narratives on both sides: it emphasizes the scale of cross‑border infrastructure, enforcement, and cooperation challenges (seen in immigration and encounter statistics cited in policy discussions) and buttresses the oft‑repeated image of a “long, largely peaceful and undefended” frontier [2] [8]. Yet those same policy pieces must confront practical differences along the line — from densely crossed Great Lakes and northeastern crossings to sparsely patrolled Arctic reaches — matters the raw distance alone does not capture [2] [8].
5. Bottom line
Across authoritative mapping agencies and official commissions the Canada–U.S. boundary is the planet’s longest bilateral international border when measured end‑to‑end (≈8,891 km / 5,525 mi), composed of a roughly 6,416 km contiguous U.S. segment and a roughly 2,475 km Alaska segment; alternative published totals exist but reflect methodological choices rather than substantive challenges to the overall ranking [1] [2] [3] [5].