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...