Spain launched the first official explorations of the Pacific Northwest in the latter half of the 18th century. Spanish sea captains sailed from Mexican and Californian ports to the coasts of present-day Washington State and Canada’s British Columbia, where they explored the region’s islands and channels. One of the islands the Spanish charted is San Juan Island, located today in American waters between Vancouver Island and the mainland. San Juan Island was part of a territorial dispute between Spain and Britain in the 18th century and was later the focus of a mid-19th century dispute between American and British occupiers. The island’s American and English Camps on opposite ends of the island are a National Historic Landmark and part of the San Juan Island National Historical Park.

Spanish exploration in the Pacific Northwest began in the 1770s, around the time Spain permanently settled Alta California. Spanish naval officer Juan Josef Pérez Hernández captained the first official European voyage to the Pacific Northwest in 1774. Spain was eager to establish its claim to the region, where it competed with Russia and England for land and access to trade with the First Nations people. The competition between England and Spain came to a head during the Nootka Crisis of 1789. Both nations tried to settle in the Nootka Sound on the west coast of Vancouver Island and this contest nearly led to war between them. During the crisis years, Spain sent naval officer Francisco de Eliza y Reventa to engage the American Indian people in diplomacy and to chart the region. Between 1790 and 1793, Eliza oversaw expeditions throughout the Georgia and Juan de Fuca straits, charting and naming the islands there, including San Juan Island. In the Nootka Conventions that resolved the crisis, Spain and England agreed to suspend official colonization in the Pacific Northwest, but to allow their citizens’ settlement and trade to continue. The United States received the Oregon Country, located north of the 42nd Parallel, from Spain in 1819, but Britain and the United States could not agree on a northern border until the Oregon Treaty of 1846.

An expedition led by British officer George Vancouver, who represented England during the Nootka Conventions, produced this 1798 map of the Pacific Northwest Library of Congress

San Juan Island became the center of another international crisis 1859 when Britain and the United States sent troops to the island to defend their claims to it. The dispute arose from the vague wording of the Oregon Treaty, which stated that the northwest boundary between the nations was in “the middle of the channel which separates the continent from Vancouver's Island.” The two nations interpreted the “channel” differently. Two major straits – Haro and Rosario -- separate the San Juan Islands from Vancouver Island and the mainland. Britain claimed that the Rosario Strait on the eastern side of the San Juan Islands was the official boundary, and the United States supported a Haro Strait boundary. The treaty did not state which nation could claim the San Juan Islands and the actual San Juan Island, uneasily occupied since 1819 by American and British settlers, became central to the fight over the international boundary.

A pig was the first and only casualty of the San Juan Island affair. Called the Pig War, it began after an American settler shot a pig that belonged to an employee of the British Hudson’s Bay Company when it wondered into the American’s garden in 1859. The settlers’ argument over legal compensation for the pig turned regional tensions over the northwest boundary into an international dispute. Britain and the United States sent troops to occupy the northern and southern ends of the island, which are today the historical English and American Camps. The two nations kept a military presence on the island for 12 years until they signed the Treaty of Washington in 1871. Kaiser Wilhelm I of Germany presided over the treaty and ruled in favor of the United States. The Americans took possession of the island in 1872 when Britain peacefully withdrew its troops, and the San Juan Islands, including San Juan Island, are part of the United States today.

San Juan Island National Historical Park interprets the history of the island and the buildings that contribute to the historic significance of the park’s American Camp and English Camp National Historic Landmark. The park is split into two parts that are located on opposite ends of the island, where the British and American forces were stationed during the Pig War. The American Camp Visitor Center and the English Camp Royal Marine Barracks offer visitors indoor learning opportunities, and both Camps have public hiking trails, history walks, and beaches. San Juan Island is only accessible by boat or plane, and there are public ferry options for visitors.