1842 border resolution between U.S. and British North American colonies (now Canada)
Resolved longstanding U.S.-British colonial border disputes arising from the ambiguous 1783 Treaty of Paris, averting further armed conflict.
Key Facts
- Date signed
- August 9, 1842
- U.S. signatory
- Secretary of State Daniel Webster
- British signatory
- Alexander Baring, 1st Baron Ashburton
- Extraditable crimes defined
- 7 crimes
- Primary border settled
- Maine–New Brunswick international boundary
- Border reaffirmed westward
- 49th parallel to the Rocky Mountains
By the Numbers
Location
Cause → Event → Consequence
Vague boundary language in the 1783 Treaty of Paris left the Maine–New Brunswick border undefined, fueling competing territorial claims between American and New Brunswicker settlers. These tensions escalated into the Aroostook War of 1838–1839, a series of border skirmishes that underscored the urgent need for a formal diplomatic resolution.
U.S. Secretary of State Daniel Webster and British diplomat Lord Ashburton negotiated the treaty in Washington, D.C., signing it on August 9, 1842, under President John Tyler. The agreement fixed the Maine–New Brunswick border, established the Lake Superior–Lake of the Woods boundary, reaffirmed the 49th parallel westward, defined extradition terms, provided for shared Great Lakes use, and pledged to end the high-seas slave trade.
The treaty eliminated the most contentious Anglo-American border disputes of the era, stabilizing relations between the United States and British North America. It set durable international boundaries that persist today, established early extradition cooperation, and contributed to a broader normalization of U.S.-British relations in the mid-nineteenth century.
Political Outcome
Binding treaty settled Maine–New Brunswick border, reaffirmed the 49th parallel, defined extradition crimes, and agreed to end the high-seas slave trade.
Disputed and overlapping U.S.-British territorial claims along multiple border segments stemming from the 1783 Treaty of Paris
Clearly demarcated boundaries between the United States and British North American colonies, with formal extradition and trade agreements in place