Canada shares the longest international border with the United States, stretching approximately 5,525 miles (8,891 kilometers). This extensive boundary encompasses various terrains, including forests, mountains, and lakes, as it runs from the Atlantic Ocean in the east to the Pacific Ocean in the west. The border is notable not only for its length but also for its status as the longest undefended border in the world, reflecting strong bilateral relations between the two countries. There are numerous crossings along the border, facilitating significant trade, travel, and cultural exchange, making it an essential link between the U.S. and Canada.