The 1840s were years of large territorial growth in the United States. During only four years, the amount of land that the US owned increased by 1.2 million square miles, which was a gain of more than sixty percent. The process of expansion was so rapid that many Americans stubbornly believed that the nation had a “Manifest Destiny” to dominate the continent from coast to coast. This Manifest Destiny effected all Americans regardless of regional or political lines.
However, this expansion was not a defined movement, and although it effected most people, was not supported by all Americans. Whig party leaders strongly opposed territorial growth, and even expansionist Democrats argued about how much new land should be acquired. Many supporters of this idea of Manifest Destiny believed in strong, even aggressive moves to gain more land, even if this risked going to war with other nations. Many others, who also supported Manifest Destiny, opposed the use of force to acquire these lands, and thought that other lands would join the US peacefully to gain the benefits of the republican rule. Therefore, the supporters of Manifest Destiny were many different types of people, all motivated by their individual causes.
There are several reasons why America began this expansion. In the early 1800s, many people believed that the country would weaken as it grew larger, because of the lack of effective communication and technology. But innovations in science and other areas were quickly improving. By the 1840s, steamboats had turned America’s waterways into busy commercial routes, and a network of railroads integrated eastern markets with towns and cities on the western slope of the Appalachians. In 1844, the telegraph became a more modern tool for long distance communication. The American dream of Manifest Destiny, extending the country from the Atlantic to the Pacific, now seemed more like a reality.
The US had a large amount of unoccupied land, but expansionists argued that the republic must continue to grow in order to survive. They were against the concentration of political and economic power. These expansionists believed that territorial growth would strengthen the country, and provide unlimited economic opportunities for future generations.
Expansionists were also motivated by more immediate, practical reasons. Southerners wanted to expand the slave empire, and were a main influence in the process of gaining more territory. New slave states would increase the South’s political power and serve as an outlet for the growing slave population. For American commercial interests, the expansion offered greater access to foreign markets. Some political figures, anxious to compete with Great Britain for Asia’s trade, knew of the strategic and commercial advantages of ports on the Pacific coastline of California.
Perhaps one of the most important reasons of Manifest Destiny was the growing sense of anxiety which Americans felt toward Great Britain. Americans were concerned about Great Britain’s claim to the Pacific Northwest and its close relationship with Mexico, and they viewed Great Britain as the US’s only rival for control of the Pacific coastline. This fear of British plans influenced Manifest Destiny, and caused many thoughts to shift to a military sense of the expansion. In the 1850s, having created a transcontinental empire, the United States stopped regarding British activities in the western hemisphere with importance. America was more concerned with the increasing sectional conflict over slavery, and many Americans began to reject Manifest Destiny. The expansionist movement, Manifest Destiny, faded from the national agenda in the years leading up to the Civil War.