Land for sale in San Juan County recently totaled almost $20 million and around 1,000 acres. San Juan County ranks 38th out of 39 counties in the state for the combined amount of land currently advertised for sale. Of all land and rural real estate for sale in San Juan County, Friday Harbor had 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 the 36th largest county (620 square miles) in Washington. It's located in the Puget Sound Washington region of the state.