It's not really a "preference for admission" so much as it is a cooperative program between the 5 states that allows students in the 4 without public medical schools (Wyoming, Alaska, Montana, Idaho) to pay in state tuition to attend the University of Washington, in an effort to train physicians who will return to practice in the underserved areas of those states. In addition to the IS tuition, the 4 other states also run the basic sciences curriculum for their own students, so students spend MS1 at a school in their home state (changing to be 18 months in their home state, I believe) then go to WA to complete the rest of medical school at the University of
Washington.