Chapter 13: The Age of Expansionism

Manifest Destiny

belief that the United States was divinely ordained to expand across North America, spreading republicanism and “civilization.”

Oregon Trail

principal overland route (≈2,000 mi) from Missouri to the Willamette Valley, used by hundreds of thousands of settlers.

Annexation of Texas

1845 incorporation of the Republic of Texas into the United States, a flashpoint for U.S.–Mexico tensions.

Mexican Cession

territories (California, New Mexico, etc.) ceded by Mexico in the 1848 Treaty of Guadalupe Hidalgo.

Gadsden Purchase

1853 acquisition of land south of the Gila River to facilitate a southern transcontinental railroad.

Wilmot Proviso

proposed 1846 amendment to ban slavery in any territory acquired from Mexico, sparking sectional conflict.

Polk’s Expansionism

President James K. Polk’s agenda that secured Texas annexation, the Oregon Treaty, and victory in the Mexican–American War.

“Fifty-four Forty or Fight!”

slogan demanding U.S. control of all Oregon Territory north to latitude 54° 40′, symbolizing northern expansionist zeal.

Popular Sovereignty

Lewis Cass’s (and later Stephen Douglas’s) doctrine that settlers in each territory should decide slavery’s legality.

Transcontinental Railroad

envisioned coast-to-coast rail link whose potential routes drove much of the era’s political bargaining.

Mexico (1830)

the country that held sovereignty over California, Texas (as part of Coahuila‐Texas), and New Mexico.

Republic of Texas

independent nation from 1836 to 1845 before admission as the 28th U.S. state.

Oregon Trail

the most important overland route for American migration to the Pacific Northwest.

Joseph Smith

founder of the Mormon Church in 1830, based on revelations published as the Book of Mormon.

Brigham Young

leader who orchestrated the Mormon trek to Utah following Joseph Smith’s assassination.

Northern Whigs

group that opposed President Tyler’s plan to annex Texas, fearing expansion of slavery.

James K. Polk

winner of the 1844 presidential election on an expansionist platform.

Short War Expectation

U.S. anticipated a quick, decisive victory in the Mexican–American War to secure California and New Mexico.

Great Britain

origin of early railroad technology imported to the United States.

Irish Immigration

largest group of immigrants to the U.S. between the 1830s and 1840s, fleeing famine and economic distress.

German Forty‐Eighters

German immigrants who escaped to the U.S. after the failed 1848 revolutions and economic hardship.

Polk’s Provocation

President Polk provoked the Mexican–American War by ordering troops into the disputed Nueces–Rio Grande territory.