A lot of rural med programs are going to be public schools focusing on getting students to the rural areas of their states.
The rankings I've seen for best rural med programs (which again, are rankings so take them with a grain of salt based on methodology and such) generally have University of Washington (which serves Alaska, Idaho, Montana, Wyoming), New Mexico, North Dakota, Minnesota, East Tennessee, and UNC-Chapel Hill up there as the top rural programs. AKA state schools with rural areas and a need to train students specifically to serve those rural areas.