Westward Expansion

Westward Expansion in the 1840s

The 1840s saw the next phase of rapid expansion of the territory of the United States: The Annexation of Texas in 1845, the acquisition of the Oregon Territory in 1846, and the cession of the southwest from Mexico in 1848.

The Annexation of Texas

Since the Adams-Onis Treaty in 1819, the territory of Texas was firmly in the hands of Spain and then Mexico after its independence from Spain in 1821. However, in 1836, Texas declared itself independent from Mexico and began petitioning the United States for statehood. The migration of American settlers into Texas fostered this independence movement. Mexico sent an army to quell the rebellion but was defeated by Sam Houston, and independence was granted.

Fig. 2- A portrait of President James K. Polk, who oversaw the Mexican American War and the annexation of Texas, the cession of the southwest, and the Oregon Treaty

What followed was nearly a decade of political issues and discourse over the statehood of Texas. The issue of Texas became a point of contention between the Whig Party which opposed the annexation, and the Democratic Party in favor. The main problem was slavery. In 1820, Congress passed the Missouri Compromise, establishing a boundary of which territories could have slaves and which could not. Northern Whigs feared Texas could create several slave states, upsetting the political balance in Congress.

Nevertheless, by 1845 the Democrats won out, and on his last full day in office, President John Tyler accepted the Texas annexation. His successor, President James K. Polk, upheld the annexation. Though the annexation was resolved, border disputes continued between the United States and Mexico, erupting in the Mexican American War in 1846.

The Oregon Treaty (1846)

After the War of 1812, Britain and the United States negotiated a northern border between British-held Canada and the United States along the 49-degree line of latitude to the Rocky Mountains. The region of the Rocky Mountains was jointly held by both nations, allowing for passage throughout.

Over the decades, however, this deal became less attractive to both nations as the region's resources became more accessible and valuable. Negotiations began in the early 1840s, but Britain held firm to wanting the borderline to continue the 49-degree line. In contrast, American expansionists wanted a border farther north along the 54-degree line. In June 1846, the U.S. and Britain signed the Oregon Treaty, establishing the northern border as the 49-degree line to the Pacific Ocean.

Mexican Cession of the Southwest (1848)

In 1848, The United States defeated the Mexican Army, and the Mexican American War ended. The Treaty of Guadalupe Hidalgo ended the war. In this treaty, Mexico ceded all claims to Texas, created a southern border along the Rio Grande, and Mexico gave up claims of Utah, Arizona, New Mexico, California, Nevada, and parts of Oklahoma, Colorado, Kansas, and Wyoming to the United States.

Fig. 3 - "American Progress" by John Gast encapsulates the images and imagination of Westward Expansion in the 1800s.

Causes of Westward Expansion

Manifest Destiny was not a cause of Westward Expansion, as by the time it was used, the expansionist movement was already occurring. The causes of Westward Expansion were mainly economic factors of the western lands and technological changes that allowed for quick adaptations to the new regions.

The Effects of Westward Expansion

With its vast economic opportunities, Westward Expansion reaffirmed to many Americans that the United States was a land of opportunity. As more Americans moved west, the effects of westward expansion were beginning to be felt throughout American society.

These new territories gave the United States access to vast amounts of natural resources and gave economic opportunities to millions of Americans. It also brought in hundreds of thousands, if not millions, of other immigrants seeking an opportunity. Thousands of Mexican migrants moved into the Southwest to work on cattle ranches, farms, and mines. Thousands of Chinese immigrants came to work on railroads. The lure of new opportunities brought new European migrants to the shores of the United States. In reaction, in the mid to late 1800s, the United States passed discriminatory immigration laws.

Westward Expansion and Slavery

Ironically, the expansion sparked sectional conflict as the nation was unifying vast territories. The debates over whether territories should be allowed to have the institution of slavery revived old southern fears of congressional and federal power. Throughout the expansion era, Congress tried to quell these fears and attempted to find a compromise. Legislation such as the Missouri Compromise of 1820, which designated a line of demarcation between what territories could and could not have slaves, held the nation together as pro-slavery and abolitionist movements grew. The annexation of Texas in 1845 brought up the issue again, as Northern abolitionists felt that many slave states could be created from the territory. Balanced by the admission of Oregon territory as a free region, the issue was only pushed aside until the subsequent territorial dispute: The Kansas-Nebraska Act of 1854.

Fig. 4- A map of the Kansas-Nebraska Act.

For all its economic benefits, Westward Expansion had the unintended consequence of being one of the main catalysts of the American Civil War, as the strain of expansion pressed on the economic and social wound of slavery.