Which U.S. Border Is Longer: Canada or Mexico?

By the Numbers

• U.S.–Canada: 5,525 miles (8,891 km) — world's longest international border. Includes 1,538 mi Alaska–Yukon/BC.
• U.S.–Mexico: 1,954 miles (3,145 km) — Rio Grande (1,255 mi) + land (699 mi).

The U.S.–Canada border is 2.8× longer.

Why the Difference?

• Canada spans the continent east-west; border follows 49th parallel (1783/1818 treaties) + natural features (Great Lakes, St. Lawrence, Rockies).
• Mexico border follows Rio Grande (natural) then straight lines (Gadsden Purchase 1854). Shorter continental width.

Coastline Bonus

If maritime boundaries count: US–Canada adds ~2,000 nm (Dixon Entrance, Juan de Fuca, Gulf of Maine, Beaufort Sea). US–Mexico adds ~500 nm (Pacific, Gulf).

Land or water, Canada wins by a wide margin.