The Oregon Treaty of 1846 established the boundary between British North America and the United States at the 49th parallel, but the interpretation of that boundary included ambiguities that caused disputes in the years that followed. The San Juan Islands, lying between Vancouver Island and the mainland, were particularly contentious. Both American settlers and British authorities claimed the islands, leading to provocative interactions. The situation grew more intense when an incident involving a pig led to the involvement of military forces from both sides, highlighting the absurdity and seriousness of the territorial dispute during this period. Jurisdiction over this area remained contested due to unclear definitions in the treaty, igniting local conflicts that required federal intervention as tensions escalated. American settlers sought to establish their presence, often supported by the U.S. government, while British settlers defended their claims with equal fervor.

In 1859, the dispute reached a boiling point, causing alarm on both sides of the border. The presence of both American and British troops in the area led to heightened military alertness, bringing the situation to the brink of armed conflict. The fear of war loomed, especially given previous diplomatic tensions between the two nations. Despite the heated atmosphere, both countries sought diplomatic resolution, eventually leading to a negotiated settlement several years later, after the issue was referred to a joint commission for arbitration.