UPSC Prelims 2024 Q79: Longest International Border — Explained
The longest border between any two countries in the world is between:
- Canada and the United States of America
- Chile and Argentina
- China and India
- Kazakhstan and Russian Federation
Answer: (a) Canada and the United States of America
Statement-wise explanation
- a: correct — The Canada–United States boundary is about 8,891 km (5,525 miles) long, according to the International Boundary Commission that maintains it. That figure has two parts: the boundary south of Canada with the lower 48 US states, and a separate 2,475 km (1,538 miles) segment with Alaska. Taken together, no other pair of countries shares a longer border. It is also often called the world's longest undefended (non-militarised) border.
- b: incorrect — The Chile–Argentina border mostly follows the crest of the Andes and is about 5,300 km long (5,308 km is the figure most often given). That makes it the longest border in South America. It is still well short of the Canada–US boundary and the Kazakhstan–Russia boundary.
- c: incorrect — The Ministry of Home Affairs puts the India–China border at 3,488 km. It runs along Ladakh/Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh. It is not even India's longest border: the border with Bangladesh is longer, at 4,096.7 km.
- d: incorrect — The Kazakhstan–Russia border is very long. Sources give between about 6,800 km and 7,600 km, and it is the world's longest continuous land border. Still, it is shorter than the Canada–US total of 8,891 km once the Alaska segment is counted, so it comes second.
How to eliminate
This question cannot be solved by wording tricks, because all four options are just pairs of countries. A little ranking logic still helps. India–China can go first. The MHA figure is 3,488 km, and India's longest border is with Bangladesh (4,096.7 km), so India–China is too short to be the world's longest. Chile–Argentina is long but thin: it follows the length of one mountain chain, about 5,300 km. That leaves the two pairs of very large countries. The trap is Kazakhstan–Russia, which is the longest CONTINUOUS land border. The deciding fact is that the Canada–US total of 8,891 km includes the 2,475 km Alaska segment, and that pushes it above every other pair. Remember: Canada–US 8,891 km first, Kazakhstan–Russia about 7,600 km second, Chile–Argentina about 5,300 km third.
Know more
How border-length questions work
A border's length depends on what you count. Do you count one stretch or several? Do you include water boundaries? At what scale was it measured? That is why sources disagree. UPSC usually tests the widely accepted ranking, not exact figures.
World's longest borders between two countries
| Rank | Border | Approx. length | Note |
|---|---|---|---|
| 1 | Canada–USA | 8,891 km | Two segments: south of Canada (with the lower 48 states) + Alaska (2,475 km) |
| 2 | Kazakhstan–Russia | ~7,000–7,600 km | Longest continuous land border |
| 3 | Argentina–Chile | ~5,300 km | Follows the Andes crest and the drainage divide |
Canada–USA boundary features
- Much of the eastern boundary runs through water: the St Lawrence River and four of the five Great Lakes. Lake Michigan lies entirely inside the USA.
- West of the Lake of the Woods, long stretches follow the 49th parallel.
- The International Boundary Commission keeps a cleared strip, or 'vista', 6 m (20 feet) wide along the land boundary. It also maintains more than 8,000 monuments and reference points.
India's land borders (MHA)
India has 15,106.7 km of land border with seven countries:
| Neighbour | Length |
|---|---|
| Bangladesh | 4,096.7 km |
| China | 3,488 km |
| Pakistan | 3,323 km |
| Nepal | 1,751 km |
| Myanmar | 1,643 km |
| Bhutan | 699 km |
| Afghanistan | 106 km |
The India–China border is not fully demarcated. In practice, the Line of Actual Control (LAC) works as the boundary. The Indo-Tibetan Border Police guards it.
NCERT Concepts to Revise
- Great Lakes of North America: Much of the eastern Canada–US boundary runs through four of the five Great Lakes, which is part of why that border is so long.
- Line of Actual Control: The India–China border is not fully demarcated; the LAC is the working boundary, which explains why the 3,488 km figure is an official estimate.