The longest undefended border in the world, 5,525 miles (8900 km) long. Citizens of the United States and Canada may cross the border between their countries freely without a passport, stopping only for customs inspections. It wasn't always that way; it took 150 years of wars, treaties, and diplomatic wrangling to achieve this supreme symbol of international amity.

The principal cause of the 1755-1763 French and Indian War was control of territory between New France and Great Britain's colonies in North America. Great Britain, having defeated the French, received all of New France. King George III issued a Proclamation organizing his new domain:

"The Government of Quebec bounded on the Labrador Coast by the River St. John, and from thence by a Line drawn from the Head of that River through the Lake St. John, to the South end of the Lake Nipissim; from whence the said Line, crossing the River St. Lawrence, and the Lake Champlain, in 45. Degrees of North Latitude, passes along the High Lands which divide the Rivers that empty themselves into the said River St. Lawrence from those which fall into the Sea; and also along the North Coast of the Baye des Chaleurs, and the Coast of the Gulph of St. Lawrence to Cape Rosieres, and from thence crossing the Mouth of the River St. Lawrence by the West End of the Island of Anticosti, terminates at the aforesaid River of St. John."1

In order to enact the Proclamation of 1763, Valentine and Collins surveyed a boundary between New York and the newly-acquired Quebec, assumed to be the 45th parallel as the proclamation specified. The 45th parallel was mentioned again in the 1774 Quebec Act:

.."bounded on the south by a line from the bay of Chaleurs, along the high lands which divide the rivers that empty themselves into the river Saint Lawrence from those which fall into the sea, to a point in forty-five degrees of northern latitude, on the eastern bank of the river Connecticut, keeping the same latitude directly west, through the lake Champlain, until, in the same latitude, it meets the river Saint Lawrence; from thence up the eastern bank of the said river to the lake Ontario; thence through the lake Ontario, and the river commonly called Niagara; and thence along by the eastern and south-eastern bank of lake Erie, following the said bank, until the same shall be intersected by the northern boundary, granted by the charter of the province of Pensylvania, in case the same shall be so intersected; and from thence along the said northern and western boundaries of the said province, until the said western boundary strike the Ohio: but in case the said bank of the said lake shall not be found to be so intersected, then following the said bank until it shall arrive at that point of the said bank which shall be nearest to the north-western angle of the said province of Pensylvania; and thence, by a right line, to the said north-western angle of the said province; and thence along the western boundary of the said province, until it strike the river Ohio; and along the bank of the said river, westward, to the banks of the Mississippi..."2

The Quebec Act was one of the Intolerable Acts passed by Parliament as punishment for the Boston Tea Party; Quebec was extended down to the Ohio River. Relations between Great Britain and its colonies only got worse, resulting in the American Revolution.

The 1783 Treaty of Paris, which ended the Revolutionary War, set the borders of the new United States, the northern portion of which was:

"...from the northwest angle of Nova Scotia, viz., that angle which is formed by a line drawn due north from the source of St. Croix River to the highlands; along the said highlands which divide those rivers that empty themselves into the river St. Lawrence, from those which fall into the Atlantic Ocean, to the northwesternmost head of Connecticut River; thence down along the middle of that river to the forty-fifth degree of north latitude; from thence by a line due west on said latitude until it strikes the river Iroquois or Cataraquy3; thence along the middle of said river into Lake Ontario; through the middle of said lake until it strikes the communication by water between that lake and Lake Erie; thence along the middle of said communication into Lake Erie, through the middle of said lake until it arrives at the water communication between that lake and Lake Huron; thence along the middle of said water communication into Lake Huron, thence through the middle of said lake to the water communication between that lake and Lake Superior; thence through Lake Superior northward of the Isles Royal and Phelipeaux to the Long Lake; thence through the middle of said Long Lake and the water communication between it and the Lake of the Woods, to the said Lake of the Woods; thence through the said lake to the most northwesternmost point thereof, and from thence on a due west course to the river Mississippi..."4

The only problem was, this description was a fantasy. Most of the area along this border was uninhabited, and its geography was poorly understood. Many of the landmarks described in the treaty simply didn't exist: There is no "water communication" between Lake Superior and the Lake of The Woods, The Mississippi River doesn't go far enough north to draw a line west from the Lake of the Woods to meet it. Further East, Massachusetts and Nova Scotia Brunswick couldn't agree which river was the St. Croix River! A former approximation of the border can be seen in the county boundaries of New Brunswick.

Anyway, the British didn't respect this treaty too well, keeping troops stationed in Detroit and Chicago, and assisting Chief Pontiac in his uprising. It wasn't until war with Revolutionary France strained Britain's military ability that they decided to buy the United States's neutrality. The product of this was the 1794 Jay Treaty. This attempted to resolve some of the boundary disputes:

..."Whereas it is uncertain whether the river Mississippi extends so far to the northward as to be intersected by a line to be drawn due west from the Lake of the Woods, in the manner mentioned in the treaty of peace between His Majesty and the United States: it is agreed that measures shall be taken in concert between His Majesty's Government in America and the Government of the United States, for making a joint survey of the said river from one degree of latitude below the falls of St. Anthony, to the principal source or sources of the said river, and also of the parts adjacent thereto; and that if, on the result of such survey, it should appear that the said river would not be intersected by such a line as is above mentioned, the two parties will thereupon proceed, by amicable negotiation, to regulate the boundary line in that quarter, as well as all other points to be adjusted between the said parties5..."

"...Whereas doubts have arisen what river was truly intended under the name of the river St. Croix, mentioned in the said treaty of peace, and forming a part of the boundary therein described; that question shall be referred to the final decision of commissioners to be appointed...The said Commissioners shall, by a declaration, under their hands and seals, decide what river is the river St. Croix, intended by the treaty. The said declaration shall contain a description of the said river, and shall particularize the latitude and longitude of its mouth and of its source.6"

But this was the one article of the Jay Treaty that was not to be fully realized. The commissioners appointed found that surveying in the far northern Appalachian Mountains wasn't practical, and so a 1798 treaty let them off the hook, stating
"...the Commissioners appointed under the fifth article of the above mentioned treaty shall not be obliged to particularize in their description, the latitude and longitude of the source of the river which may be found to be the one truly intended in the aforesaid treaty of peace under the name of the river St. Croix, but they shall be at liberty to describe the said river, in such other manner as they may judge expedient, which description shall be considered as a complete execution of the duty required of the said Commissioners in this respect by the article aforesaid. And to the end that no uncertainty may hereafter exist on this subject, it is further agreed, that as soon as may be after the decision of the said Commissioners, measures shall be concerted between the Government of the United States and His Britannic Majesty's Governors or Lieutenant Governors in America, in order to erect and keep in repair a suitable monument at the place ascertained and described to be the source of the said river St. Croix7..."

The 1814 Treaty of Ghent8 ending the War of 1812 set up several boards of commissioners to

  • decide who possessed "the several Islands in the Bay of Passamaquoddy, which is part of the Bay of Fundy, and the Island of Grand Menan in the said Bay of Fundy"
  • figure out the northern end of the line due north from the Source of the St Croix, and survey the entire boundary of New England and New York to the Saint Lawrence River. The survey line of the 45th Parallel turned out not to have been done very precisely, transferring slivers of territory between Vermont, New York, and Quebec.
  • decide who owned islands in Lake Erie, Lake Ontario, and the Niagara River.
  • clarify the border west from Sault Ste Marie to the Lake of the Woods.

While the commissioners were doing their work, another treaty was drawn up, dealing with the boundary further west. The Convention of 1818 states:

"It is agreed that a Line drawn from the most North Western Point of the Lake of the Woods, along the forty Ninth Parallel of North Latitude, or, if the said Point shall not be in the Forty Ninth Parallel of North Latitude, then that a Line drawn from the said Point due North or South as the Case may be, until the said Line shall intersect the said Parallel of North Latitude, and from the Point of such Intersection due West along and with the said Parallel shall be the Line of Demarcation between the Territories of the United States, and those of His Britannic Majesty, and that the said Line shall form the Northern Boundary of the said Territories of the United States, and the Southern Boundary of the Territories of His Britannic Majesty, from the Lake of the Woods to the Stony Mountains.9"

Here is the first mention of the 49th Parallel as a border, even thought the diplomats still needed a geography lesson. The United States gave up a slice of the Louisiana Territory and Great Britain gave up the upper valley of the Red River of the North.

The northern boundary of Maine was still in dispute. When New Brunswick lumbermen entered Aroostook County in 1838 to cut logs over the winter, a Federal land agent was sent to expel them. Instead of going to cut trees somewhere else, the lumberjacks imprisoned him. New Brunswick and Maine mobilized their militias and it looked as if a war was in the offing. The result of the "Aroostook War" was the Webster-Ashburton Treaty of 1842:

"...Beginning at the monument at the source of the river St. Croix, as designated and agreed to by the Commissioners under the fifth article of the Treaty of 1794, between the Governments of the United States and Great Britain; thence, north, following the exploring line run and marked by the Surveyors of the two Governments in the years 1817 and 1818, under the fifth article of the Treaty of Ghent to its intersection with the river St. John, and to the middle of the channel thereof: thence, up the middle of the main channel of the said river St. John, to the mouth of the river St. Francis; thence up the middle of the channel of the said river St. Francis, and of the lakes through which it flows, to the outlet of the Lake Pohenagamook; thence, southwesterly, in a straight line to a point on the northwest branch of the river St. John, which point shall be ten miles distant from the main branch of the St. John, in a straight line, and in the nearest direction; but if the said point shall be found to be less than seven miles from the nearest point of the summit or crest of the highlands that divide those rivers which empty themselves into the river Saint Lawrence from those which fall into the river Saint John, then the said point shall be made to recede down the said northwest branch of the river se John, to a point seven miles in a straight line from the said summit or crest; thence, in a straight line, in a course about south eight degrees west, to the point where the parallel of latitude of 46°25' north, intersects the southwest branch of the St. John's; thence, southerly, by the said branch, to the source thereof in the highlands at the Metjarmette Portage; thence, down along the said highlands which divide the waters which empty themselves into the river Saint Lawrence from those which fall into the Atlantic Ocean, to the head of Hall's Stream; thence, down the middle of said Stream, till the line thus run intersects the old line of boundary surveyed and marked by Valentine and Collins previously to the year 1774, as the 45th degree of north latitude, and which has been known and understood to be the line of actual division between the States of New York and Vermont on one side, and the British Province of Canada, west along the said dividing line as heretofore known and understood, to the Iroquois or St. Lawrence river10."

The treaty also defined the northern boundaries of Michigan and Minnesota:

"It is moreover agreed, that from the place where the joint Commissioners terminated their labors under the sixth article of the Treaty of Ghent, to wit: at a point in the Neebish Channel, near Muddy Lake, the line shall run into and along the ship channel between Saint Joseph and St. Tammany Islands, to the division of the channel at or near the head of St. Joseph's Island; thence, turning eastwardly and northwardly, around the lower end of St. George's or Sugar Island, and following the middle of the channel which divides St. George's from St. Joseph's Island; thence, up the east Neebish channel, nearest to St. George's Island, through the middle of Lake George; -thence, west of Jonas' Island, into St. Mary's river, to a point in the middle of that river, about one mile above St. George's or Sugar Island, so as to appropriate and assign the said Island to the United States; thence, adopting the line traced on the maps by the Commissioners, thro' the river St. Mary and Lake Superior, to a point north of Ile Royale in said Lake, one hundred yards to the north and east of Ile Chapeau, which last mentioned Island lies near the northeastern point of Ile Royale, where the line marked by the Commissioners terminates; and from the last mentioned point, southwesterly, through the middle of the Sound between Ile Royale and the northwestern mainland, to the mouth of Pigeon river, and up the said river to, and through, the north and South Fowl Lakes, to the Lakes of the height of land between Lake Superior and the Lake of the Woods; thence, along the water-communication to Lake Saisaginaga, and through that Lake; thence, to and through Cypress Lake, Lac du Bois Blanc, Lac la Croix, Little Vermilion Lake, and Lake Namecan, and through the several smaller lakes, straights, or streams, connecting the lakes here mentioned, to that point in Lac la Pluie, or Rainy Lake, at the Chaudiere falls, from which the Commissioners traced the line to the most northwestern point of the Lake of the Woods,-thence, along the said line to the said most northwestern point, being in latitude 49° 23'55" north, and in longitude 95°14'38" west from the Observatory at Greenwich; thence, according to existing treaties, due south to its intersection with the 49th parallel of north latitude, and along that parallel to the Rocky Mountains.11"

Notice that the border of New York and Vermont is no longer the 45th parallel, but the inaccurate Valentine-Collins Line.

The Webster-Ashburton Treaty disposed of most of the disputes along the U.S.'s northern border, but not all of them. At the time, the U.S. and Great Britain had joint control of the Oregon Country, territory west of the Rocky Mountains but north of California. This wasn't working out to well. In 1844, after Andrew Jackson decided he didn't like the other contenders, the Democratic Party nominated a "dark horse" as its Presidential candidate: a Tennessee congressman by the name of James K. Polk. Polk was not very well known, but he was committed to the notion of manifest destiny. He decided that demanding all of Oregon (as well as Texas) would help him get elected. This uncompromising position (Fifty-four Forty or Fight!) helped Polk get enough votes to beat the Great Compromiser, Henry Clay.

Annexing Texas meant war with Mexico, and annexing all of Oregon meant war with Great Britain. So Polk proposed extending the 49th Parallel boundary west to the Pacific. The British eventually accepted, with one minor adjustment: They would not give up the southern tip of Vancouver Island. The 1846 Oregon Treaty states:

"...From the point of the forty-ninth parallel of north latitude, where the boundary laid down in existing treaties and conventions between the United States and Great Britain terminates, the line of boundary between the territories of the United States and those of her Britannic Majesty shall be continued westward along the said forty-ninth parallel of north latitude to the middle of the channel which separates the continent from Vancouver's Island, and thence southerly through the middle of the said channel, and of Fuca's Straits, to the Pacific Ocean12..."

1867 held two important events for the boundary: the Canada Act creating the Dominion of Canada as well as William Seward's purchase of Alaska from Russia. An 1825 Treaty between Russia and Great Britain had set the border of Alaska, but as we have seen before, the two parties disputed what the treaty actually meant. Most of the boundary followed the 141st meridian, but in the region of The Alaska Panhandle, the border was described as "parallel to the Coast". If you look at this convoluted stretch of the "coast", with its countless fjords and islands, you will be able to see how easily disputes could arise. The Russian maps used by the United States drew the boundary parallel to the inner coast, following all the bays and fjords, and ignoring the Alexander Archipelago. The Canadians, on the other hand, drew it parallel to the outer coast, which would have put Juneau as well as other locations for seaports in Canada. Nobody paid attention until gold was discovered in the Yukon; suddenly, Canadian access to the ocean became valuable.

In 1898, the US and Great Britian signed a treaty which would have allowed for a survey of the boundary. However, the U.S. Sentate rejected it. By this time, the United States had become the predominant industrial power in the world, and Great Britain was in an arms race with Germany. The Hay/Herbert Treaty of 1903 set up a commission, consisting of three American delegates, two Canadian delegates, and a British delegate. Theodore Roosevelt "spoke softly" to the commissioners via his delegates Elihu Root and Henry Cabot Lodge. In 1908, the commission gave all of the disputed territory to the United States.

Finally, in 1925, a treaty was signed defining the entire boundary between the two countries. The only other change chopped off the tip of Minnesota off at the Northwest Angle rather than the actual northwesternmost point of the Lake of the Woods.

The border is now defined as a chain of straight lines between 5,528 monuments (on land) and buoys (in the water). The treaty set up an International Boundary Commission which is responsible for maintaining the boundary monuments and buoys, approving construction that crosses the border, as well as who gets jurisdiction for crimes committed at the border. Another of the tasks handed to them by the treaty is to maintain a 20-foot clear cut swath along the border. This is required by the treaty, although it mars the countryside, especially in the Waterton Glacier International Peace Park.

1The Royal Proclamation, October 7, 1763 can be found at the Solon Law Archive,,
or at The Avalon Project at Yale Law School,

2Founder's Library, Quebec Act, 1774

3The name at that time for the Saint Lawrence River, from Lake Ontario to Montreal.

4Article 2, Treaty of Paris, 1783 The University of Oklahoma Law Center

5The Jay Treaty, 1794, Treaty of Amity Commerce and Navigation, found at A Hypertext on American History
This can also be found at

6Ibid., Article 5.

7Ibid, Explanatory Article.

8The Treaty of Ghent can be found at numerous locations. One such place is the Avalon Project at Yale Law School,

9Convention of 1818, Avalon Project,

10Article 1, The Webster-Ashburton Treaty. August 9, 1842, Avalon Project,

11Ibid, Article 2

12The Oregon Treaty, 1846, found at the Center for Columbia River History,


ICE Case Studies, The United States-Canada Border Dispute,

International Boundary Commission

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