Landmark Treaties

Why This Matters

Treaties are the documentary evidence of American power, ambition, and evolving relationships with the world. When you study these agreements, you're really studying how the United States grew from a fragile new nation desperate for recognition into a global imperial power. The AP exam loves to test your understanding of territorial expansion, foreign policy shifts, and the tension between isolationism and international engagement—and treaties are where all of these themes intersect.

Don't just memorize which treaty did what. You're being tested on the underlying patterns: How did early treaties reflect American weakness and dependence on European powers? When did the U.S. shift from acquiring contiguous territory to overseas empire? What role did economic interests—trade routes, ports, railroad lines—play in shaping diplomatic priorities? If you can identify what concept each treaty illustrates, you'll crush both the multiple choice and the FRQs.

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Establishing Independence and Early Survival (1783–1795)

The first treaties weren't about expansion—they were about survival. The young United States needed European powers to recognize its existence, respect its borders, and stop interfering with its trade. These agreements reveal American diplomatic weakness and the constant threat of being pulled back into European conflicts.

Treaty of Paris (1783)

• Ended the Revolutionary War and formally recognized American independence from Great Britain
• Established generous boundaries—the Mississippi River to the west, the Great Lakes to the north, and Florida to the south
• British concessions exceeded military realities—Britain wanted to end the costly war and pull the U.S. away from France

Jay's Treaty (1794)

• Resolved lingering conflicts from the Treaty of Paris, particularly British occupation of Northwest Territory forts
• Avoided war with Britain at the cost of political controversy—critics called it a sellout to British interests
• Revealed American weakness—the U.S. lacked the military power to force British compliance and had to negotiate from a position of dependence

Pinckney's Treaty (1795)

• Secured Mississippi River navigation rights and access to the port of New Orleans—critical for western farmers
• Established the 31st parallel as the boundary with Spanish Florida
• Demonstrated Spanish anxiety—Spain feared American expansion and Anglo-American alliance, making them eager to negotiate

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Continental Expansion Through Diplomacy (1803–1853)

The United States expanded dramatically not primarily through conquest, but through purchase and negotiation. These treaties reflect the ideology of Manifest Destiny and the practical reality that buying land was cheaper than fighting for it.

Louisiana Purchase Treaty (1803)

• Doubled the nation's size for approximately $15 million$—roughly 3 cents per acre
• Constitutional controversy—Jefferson, a strict constructionist, struggled to justify the purchase without explicit constitutional authority
• Eliminated French presence in North America and secured full control of the Mississippi River and New Orleans

Adams-Onís Treaty (1819)

• Acquired Florida from Spain and settled the western boundary of the Louisiana Purchase
• Transcontinental implications—Spain ceded claims to the Pacific Northwest, strengthening American position against Britain and Russia
• Spanish decline evident—Spain couldn't control Florida and faced Latin American independence movements, making sale inevitable

Treaty of Guadalupe Hidalgo (1848)

• Ended the Mexican-American War and transferred the Mexican Cession—California, Nevada, Utah, and parts of four other states
• Massive territorial gain—added over 500,000 square miles, including the gold-rich California territory
• Slavery controversy intensified—the Wilmot Proviso debate and later Compromise of 1850 stemmed directly from this acquisition

Gadsden Purchase (1853)

• Acquired southern Arizona and New Mexico for $10 million$ to facilitate a southern transcontinental railroad route
• Completed continental expansion—established the final contiguous U.S.-Mexico border
• Sectional tensions—southern politicians pushed for the purchase to ensure a railroad route through slave territory

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Resolving Conflicts and Maintaining Peace (1814–1842)

Not every treaty expanded territory—some simply ended wars or prevented them. These agreements show the U.S. prioritizing stability and economic development over territorial gain.

Treaty of Ghent (1814)

• Ended the War of 1812 with status quo antebellum—no territorial changes for either side
• Neither side "won"—but Americans celebrated it as a victory because they had survived against the world's greatest naval power
• Launched the "Era of Good Feelings"—reduced British-American tensions and allowed focus on internal development

Webster-Ashburton Treaty (1842)

• Resolved the Maine boundary dispute and established the border through the Great Lakes region
• Improved Anglo-American relations during a period of tension over Canadian rebellions and the slave trade
• Included extradition provisions and cooperation on suppressing the African slave trade

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Emergence as a Global Power (1898–1905)

The late 19th and early 20th centuries marked a dramatic shift: the U.S. stopped acquiring contiguous territory and began building an overseas empire. These treaties reflect the ideology of imperialism, the influence of Alfred Thayer Mahan's naval theories, and economic interests in Asia and Latin America.

Treaty of Paris (1898)

• Ended the Spanish-American War and transferred Puerto Rico, Guam, and the Philippines to U.S. control
• Marked the birth of American imperialism—the U.S. now possessed overseas colonies with millions of non-citizen subjects
• Sparked fierce debate—Anti-Imperialist League argued that colonialism violated American democratic principles

Hay-Pauncefote Treaty (1901)

• Gave the U.S. exclusive rights to build and control an isthmian canal
• Superseded the Clayton-Bulwer Treaty (1850) which had required joint British-American control
• Reflected British accommodation—Britain was focused on European threats and willing to cede Western Hemisphere dominance to the U.S.

Panama Canal Treaty (1903)

• Granted the U.S. control of the Canal Zone "in perpetuity" for $10 million$ plus annual payments
• Followed controversial intervention—the U.S. supported Panamanian independence from Colombia to secure the deal
• Strategic significance—the canal (opened 1914) allowed rapid naval movement between Atlantic and Pacific, fulfilling Mahan's vision

Treaty of Portsmouth (1905)

• Ended the Russo-Japanese War through Theodore Roosevelt's mediation
• Established the U.S. as international mediator—Roosevelt won the Nobel Peace Prize
• Balanced Asian powers—prevented either Russia or Japan from dominating East Asia, protecting American interests in China

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International Cooperation and Its Limits (1919–1922)

After World War I, the U.S. faced a choice: lead international institutions or retreat into isolation. These treaties reveal the tension between Wilsonian internationalism and traditional American reluctance to commit to permanent alliances.

Treaty of Versailles (1919)

• Ended World War I and imposed harsh terms on Germany—war guilt, reparations, territorial losses
• Created the League of Nations—Wilson's vision for collective security and international cooperation
• Senate rejection—reservationists led by Henry Cabot Lodge refused to ratify without amendments; the U.S. never joined the League

Washington Naval Treaty (1922)

• Limited naval construction among major powers with a 5:5:3 ratio for U.S., Britain, and Japan
• Represented arms control success—temporarily prevented a costly naval arms race
• Showed selective engagement—the U.S. would participate in international agreements that served its interests without joining permanent organizations

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Quick Reference Table

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Self-Check Questions

1. Which two treaties both resolved conflicts with Britain but produced dramatically different territorial outcomes, and what explains the difference?

2. Identify three treaties that demonstrate the ideology of Manifest Destiny. What common themes connect them?

3. Compare and contrast the Treaty of Paris (1783) and the Treaty of Paris (1898). How do these bookend treaties illustrate the transformation of American foreign policy over 115 years?

4. If an FRQ asked you to explain the shift from continental expansion to overseas imperialism, which treaties would you use as evidence, and what turning point would you identify?

5. Why did the Senate ratify the Washington Naval Treaty but reject the Treaty of Versailles? What does this reveal about American attitudes toward international commitments in the 1920s?