Mexican-American War was fought between 1846 and 1848 and marked the first war for the United States that was primary fought on foreign soil. The war was initiated by the United States, with President Polk seeking to expand American territory under the doctrine of manifest destiny. This doctrine argued that the United States should spread across all of North America, and was used as justification military action such as this one. The major outcome of the war was a massive expansion of the United States across much of what is now the American Southwest. The U.S. absorbed New Mexico, Arizona, Nevada, Utah and California as the result of this conflict, something that shapes America in many ways today (History.com, 2016). Background

At the outbreak of the war, Mexico held much of the territory that now comprises the U.S. southwest. Mexico was, however, a weak country. Its government was headquartered in Mexico City, removed from the territory by thousands of miles of desert. Mexico was founded in 1821 after a war of independence from Spain. The country's capital was Mexico City, as it is today, in a heavily-populated and agriculturally-rich region that was home to the Aztec Empire. Mexico had sought to encourage migration to Texas, but failed in that regard, and Texas saw more English-speaking settlers. Texas would soon break away from Mexico, as would the neighboring Republic of Rio Grande. For several years, there was ongoing tension between the United States and Mexico over the status of Texas. Mexico retained its claim to the territory, while Texans preferred annexation by the United States.

James Polk ran for President on a platform built around manifest destiny, and specifically intended to annex Texas if he won the election, which he did. This was followed in 1845 with the official annexation of Texas by the United States. Polk sought to take over much of what is today the Southwest and Oregon Territory, and moved to do just this. Initially, he offered to purchase much of this land, but that offer was rejected. His response was to move troops into a disputed area that was part of the state of Coahuila (History.com, 2016).

By this point, Mexico and the United States no longer had diplomatic relations, because the U.S. and Texas had signed an agreement for the annexation of Texas. Mexican forces were also active in the disputed area, and the U.S. declared war on Mexico on May 13, 1846, marking the official beginning of the conflict (Department of State, 2016). Mexico's military was relatively weak, and there was not much of it along this border area. The United States was able to enjoy a series of defeats owing to its drastically superior manpower in the early stage of the conflict.

There were three fronts at this point of the war. Stephen Kearny captured Santa Fe, Zachary Taylor invaded Mexico from the north, and Commodore Sloat invaded California from the sea. All three won their respective battles. Even as the Americans pushed southward, the Mexicans did not surrender. General Winfield Scott led a mission to capture Mexico City, landing at Veracruz and marching from there (Smithsonian, 2016). Mexico City was captured in September, 1847.

Treaty of Guadalupe-Hidalgo

The war was ended in February 1948 with the signing of the Treaty of Guadalupe-Hidalgo. This treaty ceded vast amounts of Mexican territory to the United States, including most of what it now the Southwest. The United States gave Mexico some money - $15 million -- for this territory. The issue with the Treaty was that by that time, the expansionist sentiment had grown. Expansionists wanted the United States to annex all of Mexico. This was something of a new take on manifest destiny, but the country was relatively young, clearly not capable of resisting American military might, and many within Congress, including Polk's own Democrats, where agitating for an expansion of the conflict to take over the entire country.

Thus, the decision to sign the Treaty was controversial. On one hand, it vastly extended American territory and avoided dragging out an extended war into more populous territories, and the mountains, densely-forested territories in the southern part of the country. Polk saw little advantage in maintaining the conflict, even though he himself was an expansionist (U.S. State Department, 2016). Thus, the Treaty was signed. The war ended, and the United States map was dramatically reshaped.

Outcomes

The most obvious outcome for the United States was the change to the physical geography. Lands that would become...

The map of the U.S. was getting nearer to completion in its modern form. Further, this conflict was the last great opportunity that the U.S. had to push southward. Having passed up that opportunity, the Treaty of Guadalupe-Hidalgo essentially defined the southern border of the U.S. as it stands today.
These territories would go on to be very important to the United States. California had oil, and fertile agricultural land. The other states had mining interests. Utah was opened up to the Mormons, a lasting cultural and political impact of its conquest in this war. Further, Texas had oil as well. This oil forms a major economic boost to the U.S. for most of the 20th century and into the 21st century. Economically, the war provided the U.S. with a couple of its largest, most wealthy states, and states that would eventually absorb millions of migrants from other parts of the country. While initially the manifest destiny vision was for agriculture, resource industries would be just as important in this expansion.

There were further implications for the idea of manifest destiny. There was a longstanding dispute at the time between Britain and the U.S. with respect to the Oregon territory. The British were claiming as far south as the Columbia River, some Americans as far north as 54'40. After the Treaty, Polk turned his attention to this dispute. He wanted an expansionist victory, but did not see the value in provoking an extended conflict with Britain, so ordered negotiations to begin. The Oregon Treaty was signed in June, 1846, defining the boundary between Britain (now Canada) and the U.S. along the 49th parallel. Manifest destiny would be invoked a couple of more times, such as in the Spanish-American war when the U.S. seized multiple properties from Spain, and in the debate over the status of Hawaii.

Furthermore, the War helped to shape the relationship between Mexico and the United States. Especially in the border regions, this relationship has at times remained contentious. While not the point of armed conflict, even today there is frequently a climate of mistrust both on the part of Mexicans who are resentful of the U.S. but also on the part of Americans, some of whom to this day maintain mistrust of Mexicans.

The cultural sphere is one of the most important areas where the Mexican-American War shaped the U.S. All of these territories maintain their Spanish names today, and they also maintain their Spanish identities. The Chicano people are the Spanish speakers who ended up in what was now American territory, and they form an important part of this region's cultural heritage, completely distinct from more recent Spanish-speaking arrivals. But these states are still the ones that receive the lion's share of Mexican and Central American immigrants. In essence, they have remained as bilingual and bicultural places throughout their histories. Without this War, the western expansion of the U.S. would have been to the north. The U.S. may or may not have contested Britain for its lands, but in any case would have ended up with much less Spanish cultural influence without the former Mexican territories. Indeed, Polk would have had much less incentive to sign the Treaty of Oregon, and the U.S. likely would not have had the Alaska Purchase either.

Ultimately, the Pacific component of the might have been a relatively narrow version compared to what we have today, from northern California at best to the 49th parallel. The U.S. would have been more monocultural, but it would also have been much more focused on the east coast, without a large and wealthy territory on the Pacific to serve as balance. The Mexican War allowed the U.S. to reach the Pacific with its own territory (the Oregon territory was shared with Britain at the time). Missouri and Arkansas were as far west as the U.S. went at the time, but ultimately having a large Pacific territory taken in the span of six months provided the impetus for the westward expansion that followed, and the eventual creation of the Plains and mountain states. The Homestead Act followed within a few years to encourage this settlement of the West. Not surprisingly, this did not have positive outcomes for the native peoples of these regions, who were subject to genocide, and who lost their primary food source, the buffalo.

Expansionists, while perhaps disappointed at not taking all of Mexico, now saw a clear pathway for westward expansion across to the Pacific, the fulfilment of most…