Western Expansion, Manifest Destiny, and the Mexican-American War

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Causes and Assumptions of Manifest Destiny


Manifest Destiny was driven by the belief that Americans were destined to expand across North America. Key causes included the desire for economic opportunities, land for farming, and the spread of American ideals. Assumptions included the belief in the superiority of American culture and institutions, and the idea that expansion was justified and inevitable.

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What were the causes of Manifest Destiny?

The social movement of Manifest Destiny that evolved in the 1800s had no one cause, and no one definition.  It did not start on a Tuesday and end on a Wednesday.  It became, over time, a generally accepted justification for conquering western lands from both Mexico and Native Americans.

I remember a quote from one of my college professors very well.  He wrote it on the board and made us prove it or refute it:

Expansion, in the history of Western Civilization, was most often motivated by greed, and justified by religion

I think we can put Manifest Destiny in this category.  To take the land and resources that other peoples had owned for hundreds, even thousands of years, a social justification had to emerge.  Simple racism or nationalism wasn't enough.  We needed God's blessings.  While it is difficult to find a passage in the Bible that tells Americans they are blessed to take North America, it was nevertheless easy to believe that we were God's chosen people, and so that was used to justify every conquest, every subjugation in the American west.

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What were the causes of Manifest Destiny?

Manifest destiny was caused by the fact that the American people were historically connected to English civilization.  This gave them a sense of superiority over the other peoples who lived in North America.

Because of the fact that they were white and civilized, the Americans felt superior to the Indians.  They felt that the Indians' lack of civilization proved that they were inferior.  Therefore, the Americans thought, they deserved to conquer Indian lands.

Because the Americans were English and England was powerful, they felt superior to the Spaniards of Mexico and Cuba and other places.  They knew that their country was superior to Spain and they felt that their Protestant religion was superior to Catholicism.

So, because of their origins in white, English civilization, the American people felt they were superior to others and deserved to dominate all of North America.

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What were the causes of Manifest Destiny?

Manifest Destiny refers to the desire of the United States to spread from the Atlantic Ocean to the Pacific Ocean. In the 1800s, the United States began to grow as a country.

Once the Louisiana Purchase was made, the United States controlled most land from the Atlantic Ocean to the Rocky Mountains. People began to move to these new lands. As we moved westward, we believed we were helping our country grow and our economy grow. We encountered different groups of people, mainly the Native Americans and the Mexicans, who lived very differently than we did. We believed these groups were holding back our country’s progress.

The people of our country believed our way of living was superior to the way of life of the Native Americans and the way of life of the Mexicans. We believed the Native Americans were slowing down the growth of the country. We knew the Mexicans controlled much of the land in the West. We knew we needed to control that land in order to fulfill our goal of controlling the territory between the Atlantic Ocean and the Pacific Ocean.

As a result, we pursued policies to help us control this land. The Native Americans were moved to lands west of the Mississippi River. Eventually, they were placed on reservations. We supported the people of Texas in their fight against Mexico. We were looking for a conflict with Mexico that would allow us to gain the southwest part of our country. The Mexican-American War allowed this to occur.

By 1854, we had achieved our goal of spreading from the Atlantic Ocean to the Pacific Ocean. Manifest Destiny was now complete. People who believed that is was our duty to control these areas were happy with that we gained control of these lands.

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What were the major assumptions of "Manifest Destiny"?

The two most important assumptions are the assumption that God favors some countries over others and the assumption that some races and cultures are better than others.

Manifest Destiny assumed the superiority of the Anglo-Saxon "race."  It assumed the superiority Protestantism over Catholicism and of American culture over other cultures.  It also assumed that this superiority was mandated by God.  It assumed that any country or any race that could be so clearly superior must be favored by God.  This added a moral dimension to the argument.  Manifest Destiny was not simply saying "might makes right."  Instead, it was saying that the mighty have the moral right (and even duty) to conquer the others because they have been favored by God.

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