Overview

From the early republic through Reconstruction, the United States expanded its international influence through treaties, war, and commerce. Foreign policy reflected national interests in security, territorial growth, and economic access, while diplomacy shaped outcomes during pivotal conflicts.

Key Themes and Events

• War of 1812: Caused by British interference with American shipping and frontier tensions. The war reaffirmed American independence and encouraged domestic manufacturing.
• Monroe Doctrine (1823): Declared the Western Hemisphere off-limits to new European colonization, establishing a cornerstone of U.S. foreign policy and asserting hemispheric leadership.
• Annexation and Manifest Destiny: Driven by expansionist ideology, the U.S. annexed Texas (1845), negotiated for Oregon, and acquired the Southwest through war with Mexico (1846–48).
• Mexican-American War: Sparked by border disputes and Manifest Destiny. The Treaty of Guadalupe Hidalgo (1848) added over 500,000 square miles to U.S. territory.
• Foreign Policy During the Civil War: The Union worked to prevent British and French recognition of the Confederacy. Diplomacy and antislavery appeals helped keep foreign powers neutral.
• Trade and Maritime Policy: U.S. expanded commercial links with Asia, including the opening of Japan (1854) and growing Pacific influence. Maritime law and naval development also gained strategic importance.

Quick Tip

Be able to explain the causes and consequences of the War of 1812 and the Mexican-American War. Understand the Monroe Doctrine’s long-term impact and how diplomacy shaped the outcome of the Civil War.