American History

In the late 1840s, during the administration of President James K. Polk, the boundary of the United States was finally stretched to the Pacific Ocean. As a result, three new states  California, New Mexico, and Texas  became part of the Union. The goal of this paper is to provide an explanation for how and why the territories that became these states were acquired by the United States government.

The acquisition and development of these three new states can be attributed to one main concept manifest destiny. Coined by magazine editor John L. OSullivan in 1845, the heart of this concept was that Americans had the God-given right to expand throughout the continent of North America. Other factors such as increased population, economic difficulties, and political pressure played a role in expansion, but all used the concept of manifest destiny as justification for their desire to go west.

During his campaign, Polk had pledged that he would take all of Oregon from Britain, with whom the United States shared ownership over the territory. Privately, however, Polk wanted to reach a practical compromise with the British. To that end, he offered to extend the boundary along the 49th parallel, but Britain refused. This led to Polk insisting that all of Oregon be annexed.

Thus, in his annual message to Congress in late 1845, he requested permission to give Britain notice that joint occupation of Oregon would end in one year. After a long debate, Congress granted Polk permission. The British response came in June 1846, in the form of a draft treaty offering to extend the Canadian-American border along the 49th parallel and through the main channel south of Vancouver Island. By June 18, 1846, the Senate ratified the treaty, thus completing the U.S. acquisition of Oregon.

Once the issue of Oregon had been settled, Polk turned his attention to Texas, California, and the Southwest. Texas had become a state in December 1845, despite the fact that its previous owner  Mexico  had broken off relations with the American government just two days after Polk took office. Worsening the situation was the fact that Mexico did not recognize the annexation and statehood of Texas, nor the Rio Grande boundary between itself and Texas.

Polk assessed the situation and decided the only way he could definitively secure Texas, as well as obtain both California and New Mexico, would be to goad the Mexicans into a military conflict. To accomplish this, Polk sought and gained approval from his cabinet to deliver a war message to Congress on May 9, 1846. That same day, news arrived that the Mexicans attacked American soldiers that had been stationed north of the Rio Grande River. This attack led Polk to officially declare war on Mexico on May 13, 1846.
With regard to California, Polk used the same tactic of instigating a conflict to acquire it. With government approval, John C. Fremont took a band of sixty frontiersmen on what they claimed was an exploration of California and Oregon. Starting out at the end of 1845, by mid-1846 he and his men were in the Sacramento Valley in northern California. On June 14, 1846, Americans in Sonoma proclaimed California to be an independent republic and raised a hastily designed Bear flag. By the end of the month, Fremont had endorsed the Bear Flag Republic, and was on his way to Monterey. Before he arrived there, however, the commander of the Pacific Fleet stationed there sent a party ashore to raise the American flag and declare California part of the United States. Meanwhile, American forces led by Colonel Stephen Kearny successfully ousted Mexican forces from southern California, thus completing the removal of Mexican power in California.

As previously stated, the struggle over Texas between the United States and Mexico resulted in open warfare. Beginning in the early summer of 1846, it would end the following year in September, when the capital of Mexico  Mexico City  was captured by American troops. By the beginning of 1848, the Treaty of Guadalupe-Hidalgo was signed, officially ending the Mexican War.

In the treaty, Mexico gave up all claims to Texas above the Rio Grande River and ceded California and New Mexico to America. In return, America paid Mexico 15 million and secured the claims of American citizens against Mexico up to 3.25 million. Ratified on March 10, 1848 by the Senate, the Treaty of Guadalupe-Hidalgo effectively closed the door on continental expansion.

In conclusion, President James K. Polk was able to keep his campaign promise of extending the American boundary to the Pacific Ocean. Unfortunately, Polk mistakenly assumed that the dramatic expansion of America would foster a strong sense of unity among Americans. Instead, it led to domestic strife over the issue of slavery. In spite of this, what Polk accomplished during his one term in office was exceptional. In the space of forty-eight years, America had gone from thirteen colonies into a transcontinental nation.