The Pig War was a confrontation in 1859 between the United States and the British Empire over the boundary between the US and the British Empire. The territory in dispute was the San Juan Islands, which lie between Vancouver Island and the North American mainland. The Pig War, so called because it was triggered by the shooting of a pig, is also called the Pig Episode, the Pig and Potato War, the San Juan Boundary Dispute or the Northwestern Boundary Dispute.