Well in 1818 a treaty with Britain established the boundary between Canada and the U.s. to the 49th parallel. Of this it ceded some of the purchased Louisiana territory to Britain. In return we got land south of the 49th in the previously unclaimed Oregon territories, though until the 1820 s it was a mix between British and American rule in attempt to knock the Spanish ownership out of the area. in 1821 the Adams-Onis treaty (or transcontinental treaty) ceded the spanish Oregon territory to the U.S.. It allowed New Spain to retain California, New Mexico, Texas area and gave Florida to the U.S.. New Spain eventually became Mexico.That is how we got the Oregon Territory and FloridaAlaska the U.S. bought. William Seward (Secretary of the Interior under Lincoln) bought the Russian territory for 7.2 million dollars. Of which only 5 million actually made it back to Russia. That was in 1867
genocide of the native races.