James K. Polk

Polk won the 1844 presidential election as a dark horse Democratic candidate, defeating Whig Henry Clay. He campaigned on a platform of territorial expansion, including the annexation of Texas and Oregon.

Polk completed the annexation of Texas, which had been initiated by John Tyler. Texas was admitted as a slave state, escalating tensions with Mexico over the disputed border.

Polk provoked war with Mexico over the Texas border and California. The U.S. won a decisive victory, resulting in the Treaty of Guadalupe Hidalgo, which ceded vast territories including California and the Southwest.

Polk signed the Walker Tariff, reducing tariff rates and moving toward free trade. The tariff lowered duties on imported goods and was designed to increase revenue through trade expansion.

Polk signed a treaty with Britain dividing the Oregon Territory at the 49th parallel, avoiding war. The U.S. gained present-day Oregon, Washington, and Idaho, fulfilling a campaign promise.

Polk signed the treaty ending the Mexican-American War. Mexico ceded 525,000 square miles, including California, Arizona, New Mexico, and parts of other states, for $15 million.