Below is the link to the official page for the San Juan Islands.

USA - San Juan Islands

Below is a TA's view comparing the islands and highlighting what is wonderful on each.  Note the two breaks in the URL, between com/Travel and -g58727 and between  : and  Washington; breaks must be connected when put into your browser.

 http://www.tripadvisor.com/Travel   -g58727-c102104/San-Juan-Islands:   Washington:Comprehensive.html