Canada is the largest sovereign state sharing a land border with the United States.
Canada covers about 9.98 million square kilometres, far more than Mexico, the only other sovereign country with a land border on the contiguous United States. Canada and the United States share the world’s longest international land border, measured at roughly 8,900 kilometres when the Alaska–Canada section is included.
The boundary runs between Canada and the lower 48 United States, and another section separates Canada from Alaska. It also crosses the Great Lakes and follows rivers, lakes, and surveyed lines through forests, plains, and mountain regions.
Russia is larger than Canada but does not share a land border with the United States; the two countries are separated by the Bering Strait. Cuba also has no land border with the United States, despite being geographically close to Florida.