List and explain the motives behind expansion into Texas, Oregon, and Main.

Since independence and the formation of the new state, he wanted to expand his borders to the Pacific and began with the purchase of Lusiana, with Texas President James K. Polk declares the annexation of Texas to the United States, but Mexico does not recognize this and claims Texas as his territory, in addition, Texas claims that the border is on the Rio Grande, but Mexico only recognizes a border on the Nueces River, this leads to a war in which Mexico loses half of its territory against the United States in 1847,

On February 21, 1819, Spain is forced to cede Oregon to the United States by the Treaty of Adams-Onís. Spanish settlements in the area had been scarce, small and mostly temporary, until 1846, the huge Oregon Territory, which extended from then Mexican California to Russian Alaska, was under a special regime by which the United States and the United Kingdom exercised a common domain over these lands. By the Oregon Treaty, the border was set at 49º N: the area from that latitude to 54º 40 'N was for the British and the area until 42º, for the Americans. Such limits were largely based on the Nutka conventions, which had established the border between the English and Spanish territories.

In December 1819 Maine asked Congress to be admitted to the Union, and in 1820 it was admitted under the Missouri commitment. When Maine gained its independence, much of the territory was still unexplored; For this reason, a dispute arose over the establishment of the border separating Maine from the Canadian province of New Brunswick. The problem was solved in 1842 by the Webster-Ashburton Treaty