ODOT region map
The Oregon Department of Transportation has a helpful map that divides Oregon into a few geographical "regions," paying attention to barriers between populations such as mountains, etc. This is not based on population density, it is based on the "natural" way there are barriers between Oregonians based on the "lay of the land."
The link address is: http://www.oregon.gov/ODOT/TD/TDATA/gis/odotmaps.shtml#ODOT_Region_Maps
