The Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

–United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 border

Border

Borders define geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states and other subnational entities. Some borders—such as a state's internal administrative borders, or inter-state borders within the Schengen Area—are open and...

, officially known as the International Boundary, is the longest border in the world. The terrestrial boundary (including small portions of maritime boundaries on the Atlantic

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, Pacific

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, and Arctic

Arctic Ocean

The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

 coasts, as well as the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

) is 8,891 kilometers (5,525 mi) long, including 2,475 kilometres (1,538 mi) shared with Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

. It is Canada's only land border, and Canada is by far the largest nation having a land border with only one country.
The current border originated with the Treaty of Paris

Treaty of Paris (1783)

The Treaty of Paris, signed on September 3, 1783, ended the American Revolutionary War between Great Britain on the one hand and the United States of America and its allies on the other. The other combatant nations, France, Spain and the Dutch Republic had separate agreements; for details of...

 in 1783, which ended the war between Great Britain

Kingdom of Great Britain

The former Kingdom of Great Britain, sometimes described as the 'United Kingdom of Great Britain', That the Two Kingdoms of Scotland and England, shall upon the 1st May next ensuing the date hereof, and forever after, be United into One Kingdom by the Name of GREAT BRITAIN. was a sovereign...

 and the separating colonies which would form the United States.