American Manifest Destiny began in 1783 when Great Britain gave the United states all land between Atlantic ocean and Mississippi River and between the Great Lakes and Florida.
In 1803 President Thomas Jefferson bought a huge land known as The Louisiana Purchase. This doubled the size of the United states. The Louisiana Purchase stretched from the Mississippi River to the Rocky mountains and from Canada to New Orleans. He believed that the republic depended on a complete independence in hand with land ownership especially the ownership of small farms. This is why the Democratic-Republican Party of Jefferson supported him for re-election.
Between 1846-1848 Mexico and the United states fought a war in which United states defeated Mexico and took control of California, Utah, Nevada, Arizona, parts of New Mexico and Colorado. Later on the United states and Great Britain agreed to divide the state of Oregon. Spanish speakers that were already living in these lands previously governed by Mexico were invited to remain to stay and to become U.S citizens. Although they were allowed to stay they were also forced to give up lands as new settlers. Americans living in Texas gained independence from Mexico and eventually became part of the United States.
The growth of immigration from Europe into the United States was caused by a search for a better life in the West. The Western frontier offered independence and mobility for all. Many migrated westward with land ownership and farming with freedom. While in Europe large numbers of factory worker formed a dependent working class. Americans believed in the idea of Manifest Destiny. This belief contributed to American imperialism and had a significant influence on the culture of power in the United States. The Homestead Act of 1862 gave free land to anyone who farmed new territories. This triggered war with native Americans which lasted until 1890. America claimed all 48 lower states by 1900 and had gained territory in the Spanish American War that included Cuba, Puerto Rico and the Philippines.