The two countries with the longest international border are Canada and the United States, at 8,891 km (5,525 mi).
The Canada-United States border is the world's longest undefended border, stretching from the Atlantic Ocean to the Pacific Ocean. It crosses several provinces and states, including British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Maine, Vermont, New Hampshire, New York, and Michigan. The border is also home to several major population centers, including Vancouver, Seattle, Detroit, and Toronto.