San Juan Island National Historical Park preserves the sites of American and British military camps established during a boundary crisis in the Pacific Northwest. The island had long been part of the homelands and marine world of Coast Salish peoples, including Lummi, Samish, and other communities who fished, gathered, traveled, and maintained kinship networks across waterways later divided by an international border. Spanish, British, and American exploration and settlement imposed new claims without extinguishing Indigenous rights or presence.

The Oregon Treaty of 1846 extended the United States–British North America boundary along the forty-ninth parallel and through the channel separating Vancouver Island from the continent. Ambiguous wording left the San Juan archipelago disputed. The Hudson’s Bay Company established Belle Vue Sheep Farm on San Juan Island, while American settlers claimed land under United States law. On June 15, 1859, American farmer Lyman Cutlar shot a pig belonging to company employee Charles Griffin after it entered his garden. An argument over compensation escalated the unresolved sovereignty question.

U.S. General William Harney ordered troops under Captain George Pickett to the island. British warships and Royal Marines responded, and by August hundreds of American soldiers faced a far larger British naval force. Officers on both sides refused provocative orders and avoided firing. General Winfield Scott negotiated a reduction, leading to peaceful joint occupation. Americans remained at the southern camp and British Marines at the northern camp, where gardens, buildings, ceremonies, and social visits created twelve years of armed but generally cordial coexistence.

The two nations submitted the boundary to arbitration by German emperor Wilhelm I. In October 1872 his commission selected the Haro Strait channel, awarding the islands to the United States. British Marines departed that November; American troops remained until 1874. The Pig War produced no human combat deaths, but the familiar peace story can obscure Indigenous dispossession and the colonial assumption that Britain and the United States alone could decide sovereignty over the archipelago.

Congress created the national historical park in 1966 to preserve American Camp and English Camp. Remaining structures, archaeological sites, landscapes, and reconstructed features support interpretation of diplomacy, military life, settlement, and Coast Salish continuity. Prairie restoration at American Camp also protects an ecosystem shaped partly by Indigenous burning and later farming. The park commemorates successful de-escalation, yet its fuller history reaches beyond a humorous dead pig. It concerns an imprecise treaty, aggressive military decisions, officers who exercised restraint, international arbitration, settler land claims, corporate agriculture, and Indigenous peoples whose relationships to the islands long preceded and survived the imposed border.

Archaeology has helped recover differences between the two camps. English Camp included formal gardens and buildings reflecting Royal Marine routines, while the more exposed American Camp developed around United States Army needs and a windswept prairie. Surviving objects reveal supply networks, diet, recreation, rank, and contact between personnel and civilians. Park interpretation has increasingly treated Coast Salish nations as contemporary partners rather than as a preface to the boundary dispute. That shift changes the meaning of arbitration: the peaceful settlement between empires prevented war, yet it confirmed a border that divided Indigenous travel and territory. The park’s strongest lesson is consequently double—restraint and negotiation can halt military escalation, but peace between states does not automatically produce justice for everyone affected.