<P> George Vancouver explored Puget Sound in 1792 . Vancouver claimed it for Great Britain on 4 June 1792, naming it for one of his officers, Lieutenant Peter Puget . Alexander Mackenzie was the first European to cross North America by land north of New Spain . arriving at Bella Coola on what is now the Central Coast of British Columbia in 1793 . From 1805 to 1806 Meriwether Lewis and William Clark explored the territory for the United States on the Lewis and Clark Expedition . David Thompson, working for the Montreal - based North West Company, explored much of the region beginning in 1807, with his friend and colleague Simon Fraser following the Fraser River to its mouth in 1808, attempting to ascertain whether or not it was the Columbia, as had been theorized about it in its northern reaches through New Caledonia, where it was known by its Dakleh name as the "Tacoutche Tesse". Thompson was the first European to voyage down the entire length of Columbia River . Along the way, his party camped at the junction with the Snake River on July 9, 1811 . He erected a pole and a notice claiming the country for Great Britain and stating the intention of the North West Company to build a trading post on the site . Later in 1811, on the same expedition, he finished his survey of the entire Columbia, arriving at a partially constructed Fort Astoria two months after the departure of John Jacob Astor's ill - fated Tonquin . </P> <P> The earliest evidence of the name Oregon has Spanish origins . The term "orejón" comes from the historical chronicle Relación de la Alta y Baja California (1598) written by the new Spaniard Rodrigo Motezuma and made reference to the Columbia river when the Spanish explorers penetrated into the actual North American territory that became part of the Viceroyalty of New Spain . This chronicle is the first topographical and linguistic source with respect to the place name Oregon . There are also two other sources with Spanish origins such as the name Oregano which grows in the southern part of the region . It is most probable that the American territory was named by the Spaniards as there are some populations in Spain such as "Arroyo del Oregón" which is situated in the province of Ciudad Real, also considering that the individualization in Spanish language "El Orejón" with the mutation of the letter "g" instead of "j". Another subsequent theory is that French Canadian fur company employees called the Columbia River "hurricane river" le fleuve d'ouragan, because of the strong winds of the Columbia Gorge . George R. Stewart argued in a 1944 article in American Speech that the name came from an engraver's error in a French map published in the early 18th century, on which the Ouisiconsink (Wisconsin River) was spelled "Ouaricon - sint", broken on two lines with the - sint below, so that there appeared to be a river flowing to the west named "Ouaricon". This theory was endorsed in Oregon Geographic Names as "the most plausible explanation". </P> <P> The Oregon Country was originally claimed by Great Britain, France, Russia, and Spain; the Spanish claim was later taken up by the United States . The extent of the region being claimed was vague at first, evolving over decades into the specific borders specified in the US - British treaty of 1818 . The U.S. based its claim in part on Robert Gray's entry of the Columbia River in 1792 and the Lewis and Clark Expedition . Great Britain based its claim in part on British overland explorations of the Columbia River by David Thompson and on prior discovery and exploration along the Coast . Spain's claim was based on the Inter caetera and Treaty of Tordesillas of 1493--94, as well as explorations of the Pacific coast in the late 18th century . Russia based its claim off its explorations and trading activities in the region and asserted its ownership of the region north of the 51st parallel by the Ukase of 1821, which was quickly challenged by the other powers and withdrawn to 54 ° 40 ′ N by separate treaties with the US and Britain in 1824 and 1825 respectively . Spain gave up its claims of exclusivity via the Nootka Conventions of the 1790s . In the Nootka Conventions, which followed the Nootka Crisis Spain granted Britain rights to the Pacific Northwest, although it did not establish a northern boundary for Spanish California, nor did it extinguish Spanish rights to the Pacific Northwest . Spain later relinquished any remaining claims to territory north of the 42nd parallel to the United States as part of the Adams - Onís Treaty of 1819 . In the 1820s, Russia gave up its claims south of 54 ° 40 ′ and east of the 141st meridian in separate treaties with the United States and Britain . </P> <P> Meanwhile, the United States and Britain negotiated the Anglo - American Convention of 1818 that extended the boundary between their territories west along the 49th parallel to the Rocky Mountains . The two countries agreed to "joint occupancy" of the land west of the Rockies to the Pacific Ocean . </P>

In the early 1800s what four countries claimed land in oregon