and the rest of the Southwest. It also justified the taking of Native lands in the region, though this was hardly a novel development for Americans. Manifest Destiny, associated with the Democratic Party was the main issue in the election of President James K. Polk in 1844. Polk advocated both the annexation of Texas (which, it was commonly understood, would likely lead to war with Mexico) and the assertion of American claims on territory in Oregon. Under Polk's leadership, the United States went to war against Mexico, and under the terms of the treaty that ended that conflict, the nation received a vast swath of territory encompassing California and the entire Southwest.

Manifest Destiny was a belief that many Americans had that we should expand and control the land between the Atlantic Ocean and the Pacific Ocean. They believed it was our destiny to control this land.

This concept impacted us significantly because it encouraged westward expansion. The United States wanted to annex Texas as a state. While this was delayed because Texas had slavery, Texas did join the United States in 1845. The United States wanted to take over the Oregon Territory. Both the United States and Great Britain controlled this land. We agreed to split the Oregon Territory at the 49th parallel. The United States also wanted to control what is now the southwest part of our country. We went to war with Mexico over a disputed border with Texas, and from winning this war, we gained the land that now makes up the southwest part of our country.

Eventually, people believed we should spread the idea of Manifest Destiny worldwide. This led us to a war with Spain in 1898 so we could gain colonies. As a result of winning the Spanish-American War, we gained the colonies of Guam, the Philippines, and Puerto Rico. We now spread beyond our borders. This helped us become a world power.

Manifest Destiny had a big effect on expansionism both at home and abroad. Manifest Destiny refers to our desire to expand from the Atlantic Ocean to the Pacific Ocean.  Once that was accomplished, it took on an international form of expansion. There are several examples of Manifest Destiny at work.

There are several examples of domestic expansion. When Texas got its independence from Mexico, we wanted to annex Texas. While annexation was delayed for nine years because of slavery concerns, there was little doubt Texas would eventually join the United States. We also wanted to add the Oregon Country to our land. While there was some desire to add all of the Oregon Territory, going from what is now the northern border of California to the southern border of Alaska, we reached a compromise with Great Britain that split the territory at the 49th parallel. Thus, we added what is now called the Pacific Northwest to our country. Finally, we had our eyes on what is now the southwest region of the United States. We went to war with Mexico to add this land to our country.

By 1853, we had acquired all the land that currently makes up the lower 48 states. People began to believe we should also expand internationally. Since almost all desirable lands were already colonized, we would most likely have to go to war in order to expand beyond our borders. We ended up fighting Spain in the Spanish-American War in 1898 to accomplish this goal. As a result of this war, we got Puerto Rico, Guam, and the Philippines as United States colonies. We now had taken the idea of Manifest Destiny to an international level.

Manifest Destiny was the nineteenth-century concept that the United States had the right and "destiny" to expand its borders to encompass everything west to the Pacific. The phrase, first used by journalist John O'Sullivan, connoted American racial and cultural supremacy, and trumpeted the uniqueness of American democracy. It was a powerful ideology that drove the rapid expansion of the United States in the 1830s and 1840s, a period that witnessed the annexation of Texas, the settlement of a border dispute with Great Britain in the Oregon Territory, and the conquest of a vast expanse of land controlled by Mexico. Clearly, Manifest Destiny shaped the physical expanse of the United States. In many ways, though, it was one iteration of a persistent idea in American history—the idea of American exceptionalism. This concept was influential in promoting American imperialism and in U.S. global leadership during World War II and beyond. The ambition and the self-confidence central to Manifest Destiny have remained important in American history.

The philosophical underpinnings behind the notion of Manifest Destiny date back to the first Puritan settlers, such as John Winthrop, and his group’s explicit desire to build “a new Jerusalem,” or a “Shining City on a Hill.” The belief that America and its Puritan founders had a moral right and obligation to invent a better, purer world, informed the notion of what came to be known as “American Exceptionalism,” which is the belief that buttressed Manifest Destiny, and drove our foreign policy during the 19th century. 

Manifest Destiny implies that The United States, by its very nature, and because of its founding ideals, has a moral destiny to rule the western hemisphere and to project its power and values across the continent, by force if necessary. Thomas Jefferson expanded on this notion when he envisioned a vast agricultural economy stretching from sea to sea. Jefferson's decision to go ahead with the Lousiana Purchase as president was a big first step in actualizing that dream.

In the mid-1800s, starting in 1824 with president Andrew Jackson, and continuing on with his successors, Martin Van Buren and James Polk, American leaders used the argument of inherent moral superiority and Manifest Destiny to justify their brutal treatment of Native Americans. This treatment included policies of extermination, forced migration, ethnic cleansing and the forced relocation of tribes on reservations. James Polk was a major proponent of territorial expansion both as a military leader and as a president. Although America’s westward expansion was rationalized and cloaked in terms of moral superiority, it was ironically fueled in large part by the rapacious appetite of Southern plantation owners and later, by ruthless industrialists, who believed it was their right and destiny to exploit the land and its untapped resources.

By the 1840s, the term “Manifest Destiny” had started to be coopted by mining and railroad companies, which enjoyed the political and financial support of the federal government, and could rely on the United States Army to protect its business interests not only from Native Americans who had lived on the land, but also from laborers who had the temerity to demand better pay or safer conditions.

Finally, and perhaps most notably from a foreign policy standpoint, in 1846, President Polk led America to war against Mexico, using Manifest Destiny as a rallying cry in a war that netted the United States the territories that would become Arizona, California and New Mexico. By the end of that war, the United States had mostly realized Jefferson and Madison's vision of a nation stretching from coast to coast. 

The notion of Manifest Destiny indeed played a key role in the United States' expansionist efforts.

One of the key turning points in American foreign policy was the Spanish-American War. Important political figures such as Teddy Roosevelt encouraged intervention in an ongoing Cuban revolution. Roosevelt argued that a successful revolution would give Spain a significant military advantage over the United States with Cuba as a nearby ally. 

Roosevelt used American philosophical ideals as key motivators for this intervention. Manifest destiny and the need to protect and support democracy were both cited as rationale for intervention. A pro-Spanish Cuba was seen as a potential threat to the manifest destiny Americans exercised over the continent of North America. 

In addition, yellow journalists such as William Randolph Hearst played upon these same American philosophies. In the end, intervention was approved and ushered in a new era of American invention on the behalf of key territorial interests abroad.