The following 13 U.S. states share a border with Canada: Alaska, Idaho, Maine, Michigan, Minnesota, Montana, New York, New Hampshire, North Dakota, Ohio, Pennsylvania, Vermont and Washington. Most of them have land borders, but Pennsylvania, Ohio and Michigan share only water boundaries with Canada along the Great Lakes.
Although Wisconsin and Ontario both border Lake Superior, they do not physically meet. Wisconsin's closest boundary is actually 70 miles from the Canadian border. Alaska's border with Canada is the longest at 1,538 miles, and Pennsylvania's is the shortest at 42 miles, although Idaho has the shortest land border at 45 miles.
Eight Canadian provinces border the United States: Alberta, British Columbia, Manitoba, New Brunswick, Ontario, Quebec, Saskatchewan and Yukon. Ontario has the longest border with the United States at 1,715 miles, and Alberta has the shortest at 185 miles. The United States and Canada have the world's longest international shared border at 5,525 miles.
The border between the lower 48 states and Canada was set at the 49th parallel in the 1800s, but the border is far from straight due to geographic obstacles, technological limitations of surveying at the time and territorial disputes. Although the countries have historically had very good relations, there is a 20-foot-wide cleared boundary between the two.