Summer,
I work as an ER admitting clerk at the only osteopathic hospital in the NW which is located in Portland, Oregon. I believe that all of the major specialties are represented in the Portland area, although most are family practitioners. Eastmoreland Hospital has a family practice residency and internship which takes about 7 students each year, although they may be looking to expand.
As for the rest of the NW, there are DOs scattered throughout. I have met DOs from a number of different communities from the other states as well as Oregon.
If you would like more information feel free to contact me.