San Juan Island National Historical Park ⓘ

For thousands of years, the Northern Straits region has been home to Coast Salish peoples. The temperate climate, rich soil, abundant timber, and the bounty of the sea fostered an advanced civilization that continues to thrive in our region. These resources and the way the Tribes transformed our landscape to be even more abundant is what also attracted Europeans to the islands. San Juan Island is most known for being the site of the Pig War disagreement between America and Britain. This dispute was the culmination of more than three centuries of contention over the land and resources of the Pacific Northwest.

In these pages we encourage you to get “beyond the bacon”. Our park preserves many other histories in addition to its military occupation. Explore the imperial history that led America and Britain to come to the brink of war over who would own this Indigenous land. Learn about the Hawaiian immigrants who worked for the Hudson’s Bay Company. Find out about the homesteaders who moved to San Juan Island during and after the Pig War. Examine the long history of extractive industry which began with the Royal Marines who operated the island’s first lime kilns.

Learn more about the still-unfolding history that has shaped life on San Juan Island.

The diverse ecosystems of San Juan Island National Historical Park include coastal dunes, remnant native prairies and grasslands, rocky headlands and bluffs, wetlands and lagoons, mixed conifer forests, and Garry oak woodlands. These communities provide important habitat for species the park is obligated to manage and protect. These unique habitats host a wide diversity of plants and animals but also have a high level of fragility and sensitivity. Coastal native prairies in the park are of particular importance because they are both extremely rare (less than 3% are left in their historical range) and they provide habitat for imperiled species, including the endangered island marble butterfly. Native coastal sand dunes and Garry oak woodlands similarly represent at risk and rare habitat types that have been largely lost in the Pacific Northwest and are home to a host of unique plant and animal species. Want to learn more about our unique ecosystems? Check out the recently completed Focus Condition Assessment that examines the current state of our environment. Also, you can learn about the endangered Island Marble Butterfly and park efforts to protect this species in this report .

Check out our interactive StoryMap to learn more about the important natural resources in the park.

Once common in the Salish Sea region, the sand dunes at American Camp are one of few coastal dune ecosystems remaining. Since sand dunes have become imperiled, so have the plants and animals that call the dunes home.

San Juan Island has the largest remaining population of yellow sand verbena, much of which can be found at American Camp sand dunes. This plant is found in only three sites in the United States (Washington state only) and five sites in Canada. It is imperative to the survival of the sand verbena moth. Canada has listed the moth as endangered but in contrast, it has no legal protection under the Federal or State Endangered Species programs. The American Camp sand dunes are also home to the endangered island marble butterfly and contain dense patches of tumble mustard, one of three host plants to the butterfly. American Camp and its surrounding environs are the only place left in the world that contain this rare species.

For the survival of this ecosystem, sand must be free flowing. Invasive plants that stabilize the sand (Canada thistle and Himalayan blackberry) prohibit this from happening and invite other non-native plants to take root. The NPS is concerned with the effects of dune stabilization and the potential conversion of the dunes to shrublands or grasslands. We continue to control invasive plants while making sure no harm comes to fragile plants and animals. To help protect the dunes, please do not walk within fenced areas. Walking in the dunes can trample island marble butterfly host plants.

The prairies in American Camp are some of the last surviving native prairies in Washington, constituting only 3% of its original extent. Of the roughly 700 acres of American Camp considered prairie "grasslands", most are dominated by invasive grasses and plants. Only about 30 acres of these grasslands can be considered a true native prairie. This includes portions of remnant prairie at English Camp near Young Hill.

Prairies are integral to the history of the park. For millennia, Coast Salish people maintained the prairies and encouraged the growth of native plants used for food and medicine. Within the last 200 years, prairie habitat within the park was altered by historic Euro-American farming and ranching. The newly enforced lack of fire changed the overall structure of the prairie and introduced many non-native plants.

Despite these setbacks, the American Camp prairie and grasslands are still home to a wide array of native plants and rare and unique animal species, such as the endangered island marble butterfly (Euchloe ausonides insulanus) and several varieties of camas.

Plants such as non-native grasses, Canada thistle, Himalayan blackberry, and encroaching woody species make it hard for native plant species to thrive. Park staff continually survey the prairie, mapping new and problematic invasives. Over 200 person hours are devoted per year to remove invasive plants and control small conifers that continually encroach into the prairie. To help keep new invasive plants out of San Juan Island, make sure to check your shoes and vehicle tires for hitchhiking seeds before entering the park— (especially if you’ve been in areas where invasive plants are known to occur).