The Pig War
June 15, 1859
The border between the United States and British North America through the islands between Vancouver Island and the mainland was unclear in the 1850s. Americans and the British-chartered Hudson's Bay Company both claimed San Juan Island. Then a pig wandered into a potato patch.
The pig
The US National Park Service, which runs San Juan Island National Historical Park, says the crisis came on 15 June 1859, when an American settler, Lyman Cutlar, shot a company pig rooting in his garden. When British authorities threatened to arrest him and evict Americans as trespassers, settlers asked the US Army for protection. Wikipedia tells the same story.
Troops and warships
The NPS says Brig. Gen. William S. Harney sent a company of infantry under Capt. George Pickett, who landed in late July. The governor of Vancouver Island, James Douglas, sent warships. By the end of August, the NPS says, 461 Americans with 14 field guns faced British ships carrying many more guns. The British admiral, Robert Lambert Baynes, refused to land troops, telling Douglas he would not 'involve two great nations in a war over a squabble about a pig'.
A strangely friendly standoff
The mood on the island was oddly relaxed. The NPS describes tourists arriving on excursion boats from Victoria to watch, and officers from both sides attending church together and sharing whisky and cigars. Washington and London were alarmed; President James Buchanan sent General Winfield Scott, who calmed things down. Wikipedia says the two sides agreed to a joint military occupation with no more than 100 men each.
Settlement
The joint occupation lasted years. Wikipedia says the 1871 Treaty of Washington sent the dispute to arbitration by German Emperor Wilhelm I, and in October 1872 a commission ruled for the United States. The British left, and San Juan Island became part of Washington. Today the NPS preserves both the American and English camps.