Webster–Ashburton Treaty in the context of "Saint John River (Bay of Fundy)"

The Blockade of Africa began in 1808 after the United Kingdom outlawed the Atlantic slave trade, making it illegal for British ships to transport slaves. The Royal Navy immediately established a presence off Africa to enforce the ban, called the West Africa Squadron. Although the ban initially applied only to British ships, Britain negotiated treaties with other countries to give the Royal Navy the right to intercept and search their ships for slaves.

The 1807 Act Prohibiting Importation of Slaves abolished the intercontinental slave trade in the United States but was not widely enforced. From 1819, some effort was made by the United States Navy to prevent the slave trade. This mostly consisted of patrols of the shores of the Americas and in the mid-Atlantic, the latter being largely unsuccessful due to the difficulty of intercepting ships mid-ocean. As part of the Webster–Ashburton Treaty of 1842, it was agreed that both countries would work together on the abolition of the slave trade, which was deemed piracy, and to continue the blockade of Africa. US Navy involvement continued until the beginning of the American Civil War, in 1861. The following year, the Lincoln administration gave the UK full authority to intercept US ships. Slavery was not abolished in the United States until 1865, when Congress ratified the 13th Amendment. The Royal Navy squadron remained in operation until 1870.

The Convention respecting fisheries, boundary and the restoration of slaves, also known as the London Convention, Anglo-American Convention of 1818, Convention of 1818, or simply the Treaty of 1818, is an international treaty signed in 1818 between the United States and the United Kingdom. This treaty resolved standing boundary issues between the two nations. The treaty allowed for joint occupation and settlement of the Oregon Country, known to the British and in Canadian history as the Columbia District of the Hudson's Bay Company, and including the southern portion of its sister district New Caledonia.

The two nations agreed to a boundary line involving the 49th parallel north, in part because a straight-line boundary would be easier to survey than the pre-existing boundaries based on watersheds. The treaty marked both the United Kingdom's last permanent major loss of territory in what is now the Continental United States and the United States' first permanent significant cession of North American territory to a foreign power, the second being the Webster–Ashburton Treaty of 1842. The British ceded all of Rupert's Land south of the 49th parallel and east of the Continental Divide, including all of the Red River Colony south of that latitude, while the United States ceded the northernmost edge of the Missouri Territory north of the 49th parallel.