How is the border between the United States and Canada demarcated?

The west is bounded by latitude and the east by rivers and lakes.

The west and middle lines adopt latitudes, and the Great Lakes are in the east. Except for Lake Michigan, which belongs to the United States, the shipping median lines of the other four lakes serve as national boundaries.

At that time 1846, the United States and Britain agreed to take 49 degrees north latitude as the national dividing line. Canada was a British colony when the United States became independent, and later gained independence with the permission of Britain.

Extended data:

When rivers are the boundary, navigable rivers are usually bounded by the center line of the main channel, and navigable rivers are usually bounded by the center line of the river. When the river course changes due to natural action, if the river course is eroded, the boundary will also change accordingly; If the river is diverted, the boundary will not change with it and stay in the original place.

Due to historical reasons, Latin American countries use the principle of "occupation" to divide their borders, that is, the administrative divisions of the provinces in the "Spain" period are the boundaries. African and Asian countries that gained independence from colonial rule usually regard colonial borders as international borders.

In addition, there are national boundaries divided by ethnic distribution; Religious boundaries divided by residents' religious beliefs; The boundaries of power defined by war or strength.