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San Juan County

Location of San Juan County in Washington StateSan Juan County is located in the Salish Sea in the northwest corner of Washington State.  It is bordered on the northeast by Whatcom County, the east by Skagit County, the southeast by Island County, the south by Jefferson County and the southwest by Clallam County.  As of the 2010 U.S. Census, San Juan County had a total land area of 173.92 square miles and a population of 15,769.  Friday Harbor is the largest city with a population of 2,180.  Also of interest:

  • Watershed sub-basin:  San Juan Islands.
  • Larger lakes in San Juan County:  Mountain Lake, Cascade Lake, Horseshoe Lake and Spencer Lake.
  • Mount Constitution (2,407 feet) is located in Moran State Park on Orcas Island and is the highest point in San Juan County.

U.S. Census Bureau QuickFacts for San Juan County, WA

Office of Financial Management (OFM) county data for San Juan County, WA

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Related articles

A plane releases chemical dispersant to break up an oil slick on the water surface below. Photo courtesy of the National Commission on the Deepwater Horizon Oil Spill and Offshore Drilling.

A 2017 report from the University of Washington summarizes current scientific knowledge on chemical oil spill dispersants and their potential impacts on shoreline habitats in San Juan County, Washington. 

San Juan County
Chart: Local shoreline changes in King County (2012-13). Source: King County, 2014

A significant number of Puget Sound property owners have been altering their shorelines without required permits. A new report suggests that state and local regulators should increase enforcement and make penalties more costly for violators.

Nearshore habitat , Shoreline Habitats , Kitsap County, San Juan County
Cattle Point Beach, San Juan Island, WA. Photo: Travis S. (CC BY-NC 2.0)

Rising sea levels are expected to exacerbate habitat loss caused by bulkheads, according to studies in the San Juan Islands.

Species and food webs , Fishes , Nearshore habitat , San Juan County
Friday Harbor Library, photo by Kathy Ballard

The Friday Harbor Library supports the interdisciplinary science community of the Friday Harbor Laboratories, University of Washington's marine research station in the San Juan Islands of Washington.

Island County, San Juan County
Eastsound Constructed Wetland flyer

A 2014 San Juan County report addresses sustainable growth planning, pollution prevention, and mitigation actions in the Eastsound and Westcott Bay areas.

Water quality , Healthy human population , Shoreline Habitats , Nearshore habitat , San Juan County
Friday Harbor, San Juan Island. Photo courtesy of NOAA and the Pacific Tides Party.

A summary of data on ecosystems designated as Critical Areas (formerly Environmentally Sensitive Areas) in San Juan County, including recommendations for management.

San Juan County, San Juan Islands Watershed
A view from the San Juan Islands. Photo: Bureau of Land Management

The San Juan Islands National Monument was established on March 25, 2013 by the Obama administration. 

San Juan County
Floristic Atlas of the San Juan Islands, Washington screesnhot

The Floristic Atlas of the San Juan Islands was created by the University of Washington Herbarium and provides a tool for mapping and comparing the distributions of vascular plant species within the San Juan Islands of Washington. 


Plants , San Juan County

Learn more about demographics in San Juan County, Washington.  The U.S. Census Bureau published the following quick facts.

Counties, San Juan County
Camas flower in full bloom

A botanist believes Coast Salish tribes once favored small islands in the San Juan archipelago for growing camas, an important food staple. Her studies may also show the vulnerability of these relic gardens to climate change as sea levels rise.

Plants , Terrestrial habitat , San Juan County, San Juan Islands Watershed