Canada–United States border
There are two international borders between Canada and the United States: Canada's border with the northern tier of the contiguous United States to its south, and with the U.S. state of Alaska to its northwest. The section between Canada and the contiguous United States is the second-longest continuous international border in the world after the Kazakhstan–Russia border, and the two sections together form the longest border by total length.
The boundary is long. The bi-national International Boundary Commission deals with matters relating to marking and maintaining the boundary, and the International Joint Commission deals with issues concerning boundary waters. The agencies responsible for facilitating legal passage through the international boundary are the Canada Border Services Agency and U.S. Customs and Border Protection.
History
18th century
The Treaty of Paris of 1783 ended the American Revolutionary War between Great Britain and the United States. In the second article of the Treaty, the parties agreed on all boundaries of the United States, including, but not limited to, the boundary to the north along what was then British North America. The agreed-upon boundary included the line from the northwest angle of Nova Scotia to the northwesternmost head of the Connecticut River and proceeded down along the middle of the river to the 45th parallel of north latitude.The parallel had been established in 1763 by King George III as the boundary between the provinces of Quebec and New York. It was surveyed and marked by John Collins and Thomas Valentine from 1771 to 1773. The St. Lawrence River and the Great Lakes became the boundary further west, between the United States and what is now Ontario. Northwest of Lake Superior, the boundary followed rivers to the Lake of the Woods. From the northwesternmost point of the Lake of the Woods, the boundary was agreed to go straight west until it met the Mississippi River. That line never meets the river, for the river's source is farther south, so the border was eventually drawn from the lake's northwestern point south to the 49th Parallel.
Jay Treaty (1794)
The Jay Treaty of 1794 created the International Boundary Commission, which was charged with surveying and mapping the boundary. It also provided for the removal of British forces from Detroit, as well as other frontier outposts on the U.S. side. The Jay Treaty was superseded by the Treaty of Ghent, concluding the War of 1812, which included pre-war boundaries.19th century
Signed in December 1814, the Treaty of Ghent ended the War of 1812, returning the boundaries of British North America and the United States to the state they were before the war. In the following decades, the United States and the United Kingdom concluded several treaties that settled the major boundary disputes between the two, enabling the border to be demilitarized. The Rush–Bagot Treaty of 1817 provided a plan for demilitarizing the two combatant sides in the War of 1812 and also laid out preliminary principles for drawing a border between British North America and the United States.London Convention (1818)
The Treaty of 1818 saw the expansion of both British North America and the United States, with their boundary extending westward along the 49th parallel, from the Northwest Angle at Lake of the Woods to the Rocky Mountains. While the Laurentian Divide had previously been agreed to as a border, the flatness of the terrain made it difficult to locate this line. The treaty extinguished British claims to the south of the 49th in the Red River Valley, which was part of Rupert's Land. The treaty also extinguished U.S. claims to land north of the 49th in the watershed of the Missouri River, which was part of the Louisiana Purchase. The border vista theoretically follows the 49th parallel, but in practice, the 19th-century surveyed border markers vary by several hundred feet in spots.Webster–Ashburton Treaty (1842)
Disputes over the interpretation of the border treaties and mistakes in surveying required additional negotiations, which resulted in the Webster–Ashburton Treaty of 1842. The treaty resolved the Aroostook War, a dispute over the boundary between Maine, New Brunswick, and the Province of Canada. The treaty redefined the border between New Hampshire, Vermont, and New York on the one hand, and the Province of Canada on the other, resolving the Indian Stream dispute and the Fort Blunder dilemma at the outlet to Lake Champlain.The part of the 45th parallel that separates Quebec from the U.S. states of Vermont and New York had first been surveyed from 1771 to 1773 and markers placed after it had been declared the boundary between New York and Quebec. It was surveyed again after the War of 1812. The U.S. federal government began to construct fortifications just south of the border at Rouses Point, New York, on Lake Champlain. After a significant portion of the construction was completed, measurements revealed that at that point, the actual 45th parallel was three-quarters of a mile south of the surveyed line. The fort, which became known as "Fort Blunder", was in Canada, which created a dilemma for the U.S. that was not resolved until a provision of the treaty left the border on the meandering line as surveyed. The border along the Boundary Waters in present-day Ontario and Minnesota between Lake Superior and the Northwest Angle was also redefined.
Oregon Treaty (1846)
An 1844 boundary dispute during the Presidency of James K. Polk led to a call for the northern boundary of the U.S. west of the Rockies to be 54°40′N related to the southern boundary of Russia's Alaska Territory. However, the United Kingdom wanted a border that followed the Columbia River to the Pacific Ocean. The dispute was resolved in the Oregon Treaty of 1846, which established the 49th parallel as the boundary through the Rockies.Boundary surveys (mid–19th century)
The Northwest Boundary Survey laid out the land boundary. However, the water boundary was not settled for some time. After the Pig War in 1859, arbitration in 1872 established the border between the Gulf Islands and the San Juan Islands.The International Boundary Survey began in 1872. Its mandate was to establish the border as agreed to in the Treaty of 1818. Archibald Campbell led the way for the United States, while Donald Cameron, supported by chief astronomer Samuel Anderson, headed the British team. This survey focused on the border from the Lake of the Woods to the summit of the Rocky Mountains.
20th century
In 1903, following a dispute that arose because of the Klondike Gold Rush, a joint United Kingdom–Canada–U.S. tribunal established the boundary of southeast Alaska.On April 11, 1908, it was agreed under Article IV of the "Treaty Between the United States of America and the United Kingdom Concerning the Boundary Between the United States and the Dominion of Canada from the Atlantic Ocean to the Pacific Ocean" to survey and delimit the boundary between Canada and the U.S. through the St. Lawrence River and Great Lakes by modern surveying techniques, which accomplished several changes to the border. In 1925, the International Boundary Commission's temporary mission became permanent for maintaining the survey and mapping of the border, maintaining boundary monuments and buoys, and keeping the border clear of brush and vegetation for, establishing a "border vista" extending for 3 m on each side of the line.
In 1909, under the Boundary Waters Treaty, the International Joint Commission was established for Canada and the U.S. to investigate and approve projects that affect the waters and waterways along the border.
21st century
As a result of the 2001 September 11 attacks, the U.S. declared a level 1 alert at its borders, which required intrusive inspections of all crossing vehicles and passengers, resulting in considerable border congestion. Canada's Chrétien administration worked with the U.S. Bush administration to make the border both more secure and less of an impediment for high-value goods and low-risk travellers; and on December 12, 2001, the Smart Border Declaration was signed. The agreement pioneered border innovations that have become common worldwide, such as cargo and passenger preclearance, the Free and Secure Trade program, and the NEXUS trusted traveller program. The cooperation established by the Smart Border initiative made it easier to restrict border traffic during the COVID-19 pandemic in 2020.2020–2021 closure
On March 21, 2020, in response to the COVID-19 pandemic in Canada and United States, the governments of both nations agreed to close the border for "non-essential" travel for an initial period of 30 days.The closure was extended 15 times. In mid-June 2021, the Canadian government announced it would ease some entry requirements for fully vaccinated foreign nationals', permanent residents, and Canadian citizens starting on July 5.
The closure finally expired on July 21. In mid-July, the Canadian government announced that fully vaccinated American citizens and permanent residents could visit Canada starting August 9. The American government reopened its land border to fully vaccinated Canadian citizens effective November 8. The 2020–21 closure was reportedly the first long-term blanket closure of the border since the War of 1812.
Business advocacy groups, noting the substantial economic impact of the closure on both sides of the border, called for more nuanced restrictions in place of the blanket ban on non-essential travel. The Northern Border Caucus, a group in the U.S. Congress composed of members from border communities, made similar suggestions to the governments of both countries. Beyond the closure itself, US President Donald Trump also initially suggested the idea of deploying United States military personnel near the border with Canada in connection with the pandemic. He later abandoned the idea following vocal opposition from Canadian officials.