After sending Louis and Clark on an expedition to explore the land, we slowly migrate westward, into the territory.
The Oregon treaty was created in coordination with the Red River Basin. During the convention of 1818, to create more convenience, it was negotiated that a border at 49° would separate Canada from America. It was decided in 1846 that the Oregon Territory would be split in the same manner.
The last way we gained land was through war and annexation. Mexico had newly gained independence and was allowing Americans to move in. When Americans brought slaves, they found this as treason. Mexico sent troops up to Texas to ensure we stayed in line. This resulted in many battles, most memorable being the Battle at the Alamo. After suffering many defeats, Texans captured Santa Anna, their commander, who granted us independence in exchange for his life. President Polk then allowed Texas to join, demanding Maine to become a state as well with the Webster Ash burton Treaty.
Afterward, America and Mexico went to war over how far out boundaries were set. Out troops moved to the Rio Grande, where Mexico attacked us “on our land”. We eventually won the war, expanding our borders even