How the U.S. and Britain Settled the Oregon Boundary Dispute

The Oregon Treaty of 1846 resolved decades of joint occupation and competing claims through diplomacy:

Timeline

1. 1818 Treaty (Convention of 1818): Established 49th parallel from Lake of the Woods to Rocky Mountains; agreed to joint occupation of Oregon Country (Rockies to Pacific, 42°N to 54°40'N) for 10 years.
2. 1827 Convention: Extended joint occupation indefinitely; either could withdraw with 1 year's notice.
3. 1840s — Tensions Rise: U.S. "Oregon Fever" migration; "Fifty-Four Forty or Fight!" slogan (54°40'N = Russian Alaska border); Polk elected on expansionist platform.
4. 1842 Webster-Ashburton Treaty: Settled Maine–New Brunswick border; built trust for Oregon talks.
5. June 15, 1846 — Oregon Treaty Signed: 49th parallel extended to the Strait of Georgia (Pacific); Vancouver Island kept whole for Britain (south of 49th but British); navigation rights for both in straits.

Outcome

• U.S. gained: Washington, Oregon, Idaho, parts of Montana, Wyoming
• Britain/Canada kept: British Columbia, Vancouver Island
• Avoided war; set precedent for peaceful boundary resolution

The 49th parallel remains the U.S.–Canada border from Minnesota to the Strait of Georgia.