Webster-Ashburton Treaty


The Webster-Ashburton Treaty was an agreement between the United States and Great Britain. It formally identified the border between Canada and the U.S., from the East Coast to the Rocky Mountains and resolved several other key issues.

Daniel Webster, Portrait

Daniel Webster. Image Source: Library of Congress.

Webster-Ashburton Treaty Summary

The Webster-Ashburton Treaty was an agreement between the United States and Great Britain. It formally identified the border between Canada and the U.S., from the East Coast to the Rocky Mountains. It also resolved issues related to the Caroline Affair and the Creole Mutiny. The treaty was negotiated by Daniel Webster, the U.S. Secretary of State, and Alexander Baring, Lord Ashburton.

Webster-Ashburton Treaty Facts


  • August 9, 1842 — The treaty was signed by both nations.


  • Alexander Baring, Lord Ashburton — A British diplomat who led a special mission to the United States in 1842
  • Daniel Webster — An American statesman who served as Secretary of State from 1841 to 1843.


  • The border between Maine and New Brunswick was established.
  • The border between Lake Superior and the Lake of the Woods was established.
  • The border across the 49th Parallel, to the Rocky Mountains, was clarified.
  • Crimes for extradition were defined.
  • Both nations were given navigation rights on the Great Lakes.
  • Both nations agreed to help end the International Slave Trade.


The purpose of the Webster-Ashburton Treaty was to resolve border disputes between the United States and Canada, along with other issues between the two nations, including the extradition of criminals and the International Slave Trade.

Webster-Ashburton Treaty Significance

The Webster-Ashburton Treaty, signed on August 9, 1842, helped to resolve several conflicts between the United States and Great Britain. It was a key part of establishing America’s Manifest Destiny, as it established the northern border between Canada and the U.S. from the East Coast to the Rocky Mountains.

Manifest Destiny Map, US Territorial Acquisitions, LOC
This map of the U.S. territorial acquisitions shows the border established by the Webster-Ashburton Treaty. Image Source: Wikimedia.

Webster-Ashburton Treaty History

Daniel Webster and Lord Ashburton

During Daniel Webster’s first term as Secretary of State (1841–1843), the United States faced several important foreign policy issues with Great Britain. These issues included:

  1. Disagreements over the borders between the United States and Canada.
  2. The involvement of American citizens in the Canadian Rebellion (1837), 
  3. Efforts to stop the International Slave Trade. 

On April 4, 1842, Alexander Baring, 1st Baron Ashburton, arrived in Washington, D.C., leading a special mission to the United States. Lord Ashburton was tasked with helping resolve the issues with the U.S.

Border Between the United States and Canada

The priority for Webster and Ashburton was to settle the border disputes between the United States and Canada, which stemmed from several conflicts that had arisen due to different interpretations of the Treaty of Paris (1783), which ended the American Revolutionary War (1775–1783). 

One key issue was the unclear border between the United States and Canada. Tensions escalated when officials from New Brunswick, Canada, arrested Americans in disputed areas, prompting Maine to call out its militia and seize the territory. This incident, known as the Aroostook War — even though no shots were fired — brought the issue of the border to the forefront.

Webster and Ashburton agreed to divide the disputed land, with the United States receiving 7,015 square miles and Great Britain getting 5,012 square miles. They also established the boundary line through the Great Lakes to the Lake of the Woods and ensured open navigation across several bodies of water. 

Although there were still concerns over the border between the two nations in the Oregon Territory, they decided to deal with it later and left it for future negotiations.

Alexander McLeod and the Caroline Affair

In the aftermath of the Canadian Rebellion of 1837, some of the insurgents fled to the United States and were joined by some Americans. This group occupied a Canadian island in the Niagara River and used an American ship, the Caroline, for supplies. 

Canadian troops seized the Caroline in a New York port, killed one crewman, and set the ship adrift over Niagara Falls (Caroline Affair). 

Three years later, Alexander McLeod, a Canadian, was visiting Lewiston, New York where he bragged he had been involved in the Caroline Affair. Because of this, he was arrested and charged with murder. Great Britain claimed McLeod had acted under British orders and threatened to declare war on the United States if he was executed for his alleged crimes.

The U.S. Government acknowledged that McLeod could not be tried for actions he committed under British government orders. However, government officials were unable to force the state of New York to release him. New York proceeded with the trial and McLeod was acquitted. However, tension over the situation remained. 

Webster and Ashburton discussed the principles of international law regarding the incident and issued conciliatory statements to ease the tension. The U.S. then passed a law allowing federal judges to release anyone from custody who was proven to have acted according to the order of a foreign government. Later, the U.S. and Canada established an extradition treaty.

International Slave Trade

Regarding the International Slave Trade (see Transatlantic Slave Trade), Ashburton wanted the British Royal Navy to be able to inspect American ships suspected of carrying slaves. Webster refused but did agree to have United States Navy warships patrol the coast of Africa to search for slave ships flying the American flag. Unfortunately, this agreement was not actively enforced by the U.S. until the Civil War.

Compensation for the Creole Mutiny

In 1841, the Creole, an American slave ship, was carrying 135 captive Africans to New Orleans. The Africans revolted and took control of the ship (Creole Mutiny), which sailed to the Bahamas, where slavery was illegal. Upon arrival, the Africans were freed. However, this violated international law. During the Webster-Ashburton negotiations, Britain agreed to compensate the United States with $110,330.

Impressment of American Sailors

Great Britain also agreed to stop the impressment of American sailors, which had been a significant point of contention between the two nations since the end of the American Revolutionary War. It was also one of the primary causes of the War of 1812 (see War of 1812 Overview and History).

Webster-Ashburton Treaty Vocabulary

These terms and definitions provide more context for students studying the Webster-Ashburton Treaty.


  • Alexander McLeod — A British subject arrested in New York for his involvement in the Caroline Affair.


  • Great Lakes — A group of five large freshwater lakes in North America.
  • Lake of the Woods — A lake in North America that serves as part of the boundary between the United States and Canada.


  • Aroostook War — A military confrontation in 1839 between the United States and Great Britain over the boundary between Maine and New Brunswick.
  • Canadian Rebellion of 1837 — A series of uprisings against British rule in Canada.
  • Caroline Affair — An 1837 incident where Canadian troops seized an American ship, the Caroline, resulting in the death of a crewman and heightened tensions between the U.S. and Great Britain.
  • Creole Case — A 1841 mutiny on the American ship Creole, where slaves were freed in the Bahamas, leading to monetary compensation from Great Britain.


  • Acquitted — Declared not guilty of a criminal charge.
  • Conciliatory Statements — Remarks made to ease tensions and foster goodwill.
  • Diplomat — An official representing a country abroad.
  • Extradition Treaty — An agreement between countries to hand over individuals accused or convicted of crimes.
  • Federal Judges — Judges appointed by the federal government to preside over cases involving federal law.
  • Foreign Policy — A government’s strategy in dealing with other nations.
  • Impressment — The act of forcibly recruiting sailors into a navy, particularly used by the British Navy against American sailors.
  • International Law — A set of rules generally accepted as binding in relations between countries.
  • Militia — A military force composed of ordinary citizens.
  • Mutiny — A rebellion against the lawful authority, particularly by soldiers or sailors against their commanding officers.
  • Navigation Provisions — Agreements allowing the free movement of ships in certain waters.
  • Northeast Borders — The northeastern United States and Canada boundaries.
  • Oregon Border — The boundary between the U.S. and British territories in the Pacific Northwest, left unresolved by the treaty.
  • Secretary of State — The head of the U.S. Department of State, responsible for foreign affairs.
  • Slave Trade — The transportation and sale of enslaved people (see Middle Passage).
  • Treaty of Extradition — An agreement between two nations for the mutual handing over of accused or convicted criminals.
  • Treaty of Paris (1783) — The agreement that ended the American Revolutionary War and defined the original boundaries of the United States.

Citation Information

The following information is provided for citations, including APA Style, Chicago Style, and MLA Style.

  • Article Title Webster-Ashburton Treaty
  • Date 1842
  • Author
  • Keywords Webster-Ashburton Treaty, Daniel Webster, Lord Ashburton
  • Website Name American History Central
  • Access Date June 21, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update May 29, 2024