Canadians may be experiencing increased scrutiny when crossing the boundary with the United States these days, but the border remains largely undefended and as peaceable as it was throughout the long and complicated journey of its creation.

From the time of the first successful European colonists in North America in the 1600s, a host of countries — Britain, France, Spain, Russia — moved in and out, attempting to establish footholds on the new continent.

1. 1783: Dividing line

At the end of the Revolutionary War in 1783, Britain had to recognize U.S. independence with a boundary. Britain had two border options: a line on the 45th parallel extending from the St. Lawrence to the Mississippi or a line through the Great Lakes to Lake of the Woods (then thought to be the headwater of the St. Lawrence). They chose the latter, so in 1783, the line was drawn from St. Croix Island to Lake of the Woods in 17 segments.

St. Croix

This eastern boundary point is where Samuel de Champlain camped in 1604. The St. Croix River formed the boundary between Quebec, Nova Scotia and New England in 1763.

2. 1818: Eliminating the Gap

In the Louisiana Purchase of 1803, the U.S. bought more than two million square kilometres of land, from the Mississippi River to the Rockies, from France. In doing so, the contentious gap between Lake of the Woods and the Mississippi was superseded. Since the dividing line between Rupert’s Land and the Louisiana territory approximately followed the 49th parallel and since Britain had previously said it would concede the line to the French during land negotiations in 1719, the line was drawn to the Rockies along the 49th.

Lake of the Woods

As the end point of the first stretch of the border, it left a gap of about 225 kilometres between British land to the north and the head of the Mississippi, which was the western limit of the new United States. The Brits took advantage by freely trapping in “the Gap.”

3. 1825: Protecting territory

Russia had claimed the area now known as Alaska since 1750, but when the Russians extended their claim to the northern tip of Vancouver Island in 1821, the U.S. stepped in with the Monroe doctrine, which proclaimed that European states were no longer welcome to colonize the Americas. The U.S. managed to push the Russians back to 54°40' latitude, and Britain later negotiated the border along the 141° longitude line. The U.S. bought Alaska from Russia in 1867.

4. 1846: Compromise

In 1818, the U.S. proposed extending the border to the coast along the 49th parallel, but with investments along the southern Columbia River, the British refused. So there was joint occupancy in the area known as “Oregon country” between 1828 and 1838. Many in the U.S. wanted to keep the territory, and James Polk even ran for office in 1844 with the slogan “fifty-four forty or fight.” In the end, there was compromise, and in 1846 the 49th parallel was drawn to the Strait of Georgia.

Vancouver Island

Once the 49th parallel was set as the final stretch of the border, the United States allowed for a slight deviation from the line so that the British territory would include all of Vancouver Island.

The end of the American Revolution in 1783 launched the evolution of the current border. Britain was forced to recognize American independence by creating a line on the map between its territory to the north and the United States to the south. But the border we know today was not drawn in one fell swoop. Instead, it was established in four distinct stretches, each of which took decades of negotiation and compromise.

That an 8,891-kilometre international boundary was set without conflict at a time when maps were being drafted and re-drafted as explorers such as Thompson, Mackenzie and Lewis and Clark criss-crossed the continent is a testament to the negotiating skills of the diplomats involved, says historian David Malaher, who has written extensively on the subject.

“We have to give praise to the negotiators,” he says. “With all the parties and countries involved, they managed to discuss these things without shooting anyone.”