Land for sale in Washington's San Juan County recently totaled nearly $27 million and 1,000 acres. San Juan County ranks 38th out of 39 counties in the Evergreen State for the total acreage of land currently advertised for sale. Among cities in San Juan County with farms, ranches, and rural real estate for sale, Friday Harbor featured the most land for sale. Based on its natural assets, San Juan County's economy is dependent on tourism and recreation. San Juan County is Washington's 36th biggest county (620 square miles). It's located in the Puget Sound Washington region of the state.