The Pig War of 1859 was triggered by what event?

The Pig War was a confrontation in 1859 between the United States and the United Kingdom over the British–U.S. border in the San Juan Islands, between Vancouver Island (present-day Canada) and the State of Washington. 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, and the Northwestern Boundary Dispute. Despite being referred to as a "war", there were no human casualties on either side. When news about the crisis reached Washington and London, officials from both nations were shocked and took action to calm the potentially explosive international incident.

Source: Wikipedia