The Peace Arch at the border between Surrey, British Columbia, and Blaine, Washington

The Canada–United States border, officially known as the International Boundary, is the longest international border in the world shared between the same pair of countries. The terrestrial boundary (including small portions of maritime boundaries on the Atlantic, Pacific, and Arctic coasts, as well as the Great Lakes) is 8,891 kilometres (5,525 mi) long, including 2,475 kilometres (1,538 mi) shared with Alaska. It is Canada's only land border, and Canada is by far the largest nation having a land border with only one country.

History[link]

U.S. counties sharing a land or water border with Canada

  Land border

  Water border

Sign welcoming drivers into the United States

The current border originated with the Treaty of Paris in 1783, which ended the war between Great Britain and the separating colonies which would form the United States. The 45th parallel was established as the border between Lower Canada (Quebec) and New York State (including what is now Vermont). The St. Lawrence River and the Great Lakes became the boundary between Upper Canada and the United States. The Jay Treaty of 1794 created the International Boundary Commission, which was charged with surveying and mapping the boundary. Westward expansion of both British North America and the United States saw the boundary extended west along the 49th parallel from the Northwest Angle at Lake of the Woods to the Rocky Mountains under the Convention of 1818. This convention extinguished British claims south of that latitude to the Red River Valley, which was part of Rupert's Land. The treaty also extinguished U.S. claims to land north of that line in the watershed of the Missouri River, which was part of the Louisiana Purchase; this amounted to three small areas, consisting of the northern part of the drainages of the Milk River (today in southern Alberta and southwestern Saskatchewan), the Poplar River (Saskatchewan), and Big Muddy Creek (Saskatchewan).

Disputes over the interpretation of the border treaties, and mistakes in surveying it, required additional negotiations resulting in the Webster–Ashburton Treaty of 1842. The treaty resolved the dispute known as the Aroostook War over the boundary between Maine on the one hand, and New Brunswick and the Province of Canada the other. 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 boundary along the 45th parallel had been surveyed after the War of 1812. The US Government began to construct fortifications just south of the border at Rouses Point 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. This created a dilemma for the United States 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.^[1][2]

An 1844 boundary dispute during U.S. President James K. Polk's administration led to a call for the northern boundary of the U.S. west of the Rockies to be latitude 54° 40' north (related to the southern boundary of Russia's Alaska Territory), but 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. The Northwest Boundary Survey (1857–61) laid out the land boundary, but 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. In 1903 a joint United Kingdom – Canada – U.S. tribunal established the boundary with Alaska, much of which follows the 141st meridian west.

International Boundary Commission[link]

The Oregon Country / Columbia District

In 1925, the International Boundary Commission was made a permanent organization responsible for surveying and mapping the boundary, maintaining boundary monuments (and buoys where applicable), as well as keeping the boundary clear of brush and vegetation for 6 metres (20 ft). This "border vista" extends for 3 metres (10 ft) on each side of the line. The Commission's annual budget is about $1.4 million (USD).^[3]

The commission is headed by two commissioners, one of whom is Canadian, the other American.^[4] In July 2007, the Bush administration relieved U.S. Commissioner Dennis Schornack of his post in connection with a dispute between the boundary commission and the U.S. government over private construction near the border.^[5] Schornack rejected the dismissal, saying that the commission is an independent, international organization outside the U.S. government's jurisdiction, and that according to the 1908 treaty that created it, a vacancy can only be created by "the death, resignation or other disability" of a commissioner.^[6] The Canadian government said that it was taking no position on the matter,^[7] but Peter Sullivan, the Canadian commissioner, said on July 13 that he was ready to work with David Bernhardt, a Colorado-based solicitor of the Department of the Interior, who was designated as the acting U.S. commissioner by President Bush.^[8]

Security[link]

Law enforcement approach[link]

A sign at the International Boundary in Point Roberts, Washington, warning against illegal crossing of the border

The border crossing where British Columbia Highway 37A ends at Hyder, Alaska is unmanned by United States Customs, though Canadian Customs does maintain a presence in the area.

The International Boundary is commonly referred to as the world's longest undefended border, but this is true only in the military sense, as civilian law enforcement is present. The relatively low level of security measures stands in contrast to that of the United States – Mexico border (one-third as long as the Canada–U.S. border), which is actively patrolled by U.S. customs and immigration personnel to prevent illegal migration and drug trafficking.

Parts of the International Boundary cross through mountainous terrain or heavily forested areas, but significant portions also cross remote prairie farmland and the Great Lakes and Saint Lawrence River, in addition to the maritime components of the boundary at the Atlantic, Pacific, and Arctic oceans. The border also runs through the middle of the Akwesasne Nation and even divides some buildings found in communities in Vermont and Quebec whose construction pre-dated the border's delineation. On the Maine-New Brunswick border, it divides a golf course.^[9]

The actual number of U.S. and Canadian border security personnel is classified; there are in excess of 17,000 United States Border Patrol personnel on the Mexico–U.S. border alone.^[10]

Following the September 11, 2001, terrorist attacks in the United States, border security along the International Boundary was dramatically tightened by both nations in both populated and rural areas. Both nations are also actively involved in detailed and extensive tactical and strategic intelligence sharing. It is a common misconception in the U.S. that the nineteen terrorists involved in the September 11 attacks entered the United States via the Canadian border.^[11]