By the Treaty of Paris in 1763 the whole of French America was ceded to England, which also obtained possession of Florida from Spain, in exchange for the Philippines, captured during the war.  As a compensation all the country west of the Mississippi became joined on to the Spanish possessions in Mexico.  These of course became, nominally French when Napoleon’s brother Joseph was placed on the Spanish throne, but Napoleon sold them to the United States in 1803, so that no barrier existed to the westward spread of the States.  Long previously to this, a Chartered Company had been formed in 1670, with Prince Rupert at its head, to trade with the Indians for furs in Hudson’s Bay, then and for some time afterwards called Rupertsland.  The Hudson Bay Company gradually extended its knowledge of the northerly parts of America towards the Rocky Mountains, but it was not till 1740 that Varenne de la Varanderye discovered their extent.  In 1769-71 a fur trader named Hearne traced the river Coppermine to the sea, while it was not till 1793 that Mr. (after Sir A.) Mackenzie discovered the river now named after him, and crossed the continent of North America from Atlantic to Pacific.  One of the reasons for this late exploration of the north-west of North America was a geographical myth started by a Spanish voyager named Juan de Fuca as early as 1592.  Coasting as far as Vancouver Island, he entered the inlet to the south of it, and not being able to see land to the north, brought back a report of a huge sea spreading over all that part of the country, which most geographers assumed to pass over into Hudson Bay or the neighbourhood.  It was this report as much as anything which encouraged hopes of finding the north-west passage in a latitude low enough to be free from ice.

As soon as the United States got possession of the land west of the Mississippi they began to explore it, and between 1804 and 1807 Lewis and Clarke had explored the whole basin of the Missouri, while Pike had investigated the country between the sources of the Mississippi and the Red River.  We have already seen that Behring had carried over Russian investigation and dominion into Alaska, and it was in order to avoid her encroachments down towards the Californian coast that President Monroe put forth in 1823 the doctrine that no further colonisation of the Americas would be permitted by the United States.  In this year Russia agreed to limit her claims to the country north of 54.40 deg..  The States subsequently acquired California and other adjoining states during their war with Mexico in 1848, just before gold was discovered in the Sacramento valley.  The land between California and Alaska was held in joint possession between Great Britain and the States, and was known as the Oregon Territory.  Lewis and Clarke had explored the Columbia River, while Vancouver had much earlier examined the island which now bears his name, so that both countries appear to have some rights of discovery to the district.