Convention of 1818: Fixing the US-Canada Border and Demilitarizing the Great Lakes

The Convention of 1818 (Treaty of 1818) resolved two major US-UK disputes left over from the War of 1812.

1. Northern Boundary: The 49th Parallel

• Issue: Louisiana Purchase (1803) northern limit undefined west of Lake of the Woods
• Resolution: Border set at 49°N from Lake of the Woods to the Rocky Mountains ("Stony Mountains")
• Exception: Lake of the Woods angle — NW Angle (MN) becomes US exclave
• Joint occupancy: Oregon Country (west of Rockies) shared 10 years (renewed 1827)

2. Rush-Bagot Agreement (1817, formalized 1818)

• Demilitarized the Great Lakes & Lake Champlain
• Limits: 1 vessel (100 tons, 1 gun) each on Lake Ontario; 2 each on upper lakes
• Significance: World's first modern arms control treaty; longest peaceful border
• Current: Still in force — modified 1946 for Coast Guard; RCN/USN notify each other

Additional Provisions

• Fisheries: US access to Newfoundland/Labrador coasts (renewed 1818 convention)
• Slave compensation: UK paid $1.2M for slaves evacuated during War of 1812

Legacy

The 49th parallel became the longest undefended border (5,525 mi). Rush-Bagot established naval arms control precedent. Together, they enabled 200+ years of peaceful US-Canada relations.