An Age of Expansion: 1820-1848

This era in American history was defined by significant territorial expansion, driven by ideologies like Manifest Destiny, and marked by growing tensions over slavery that would eventually lead to the Civil War.

Core Principles

Manifest Destiny: The belief that the United States was destined to expand across the North American continent.
Westward Expansion: The movement of settlers into the western territories of the United States.
Texas Annexation: The incorporation of the Republic of Texas into the United States.
Mexican-American War: A conflict between the United States and Mexico resulting in significant territorial gains for the U.S.
Oregon Question: The dispute between the U.S. and Great Britain over the territory of Oregon.
Sectionalism: Growing differences between the North and South, particularly over slavery.

Action Steps

Understand the motivations behind westward expansion.
Identify key territories acquired during this period.
Analyze the causes and consequences of the Texas Revolution and Mexican-American War.
Examine the role of Manifest Destiny in shaping national policy.
Recognize the escalating debate over slavery's expansion into new territories.

Key Terms

Manifest Destiny: The 19th-century doctrine that the United States was destined to expand its dominion and spread democracy and capitalism across the entire North American continent.
Stephen F. Austin: An American empresario who led the second, and ultimately successful, colonization of Texas by Americans in the 1820s.
Texas Revolution: A rebellion of colonists from the United States and Tejanos against the centralist government of Mexico, leading to Texas's independence.
Mexican Cession: The territory surrendered by Mexico to the United States in the Treaty of Guadalupe Hidalgo in 1848, including present-day California, Nevada, Utah, Arizona, and parts of New Mexico, Colorado, and Wyoming.
Oregon Treaty: An agreement between the United States and Great Britain that established the boundary of the U.S. and Canada along the 49th parallel.
Wilmot Proviso: A proposal to ban slavery in any territory acquired from Mexico in the Mexican-American War, which ultimately failed but intensified sectional conflict.
Popular Sovereignty: The principle that the authority of a state and its government are created and sustained by the consent of its people, through their elected representatives, who are the source of all political power. In the context of territories, it meant settlers would decide on slavery.

Pro Tips

Connect territorial expansion directly to the growing debate over slavery.
Note how economic opportunities (e.g., cotton in Texas) fueled expansion.
Recognize the role of key individuals like John O'Sullivan and James K. Polk.
Understand that 'Manifest Destiny' was a justification, not a universally accepted fact.

Pitfalls to Avoid

Viewing expansion as a peaceful or uncontested process.
Ignoring the impact of expansion on Native American populations.
Underestimating the role of slavery as a driving force behind territorial acquisition.
Forgetting the diplomatic and military complexities of acquiring new territories.

Real World Examples

American settlers moving to Texas: Motivated by land grants and economic opportunity, these settlers eventually clashed with Mexican authorities over issues like slavery and governance, leading to the Texas Revolution.
The Oregon Trail: A historic route of migration used by settlers traveling west to the Oregon Country, symbolizing the physical journey and hardship associated with westward expansion.
The Mexican-American War: A direct result of expansionist ambitions and border disputes, this war dramatically increased the size of the United States.

Timeline

1821: Mexico wins independence from Spain, opening Texas to Anglo settlement.
1835-1836: Texas Revolution; Texas declares independence.
1844: Presidential election where Texas annexation is a key issue; James K. Polk wins.
1845: Texas annexed by the United States.
1846: Mexican-American War begins; Oregon Treaty divides territory with Britain.
1848: Treaty of Guadalupe Hidalgo ends Mexican-American War; U.S. acquires vast territories.

People

John O'Sullivan: Journalist who coined the term 'Manifest Destiny'.
Stephen F. Austin: Led the first significant group of Anglo settlers to Texas.
Sam Houston: Key military leader in the Texas Revolution and first President of the Republic of Texas.
General Zachary Taylor: U.S. Army general who led troops during the Mexican-American War and later became President.
President James K. Polk: U.S. President (1845-1849) whose administration oversaw significant territorial expansion, including the annexation of Texas and the Mexican Cession.