Here are some VERY limiting factors of hosting the R100. The location would have to have 100 different shotting target areas, with with safety requires LOTS of land. The club would need to have plenty of camping available, and last but not least A HUGE ammount of club support to set up then run one of these events. I have set up and run some decent sized 3d shoots but nothing that big. It requires a LOT of time and dedication.
I can think of a couple other locations that could physically hold the shoot, however they likely do not have the manpower to do so. They also don't have as central of a location for the shoot.

If you look at the schedual you will see that we are the only real western state that has this event... So placing it between 2 large metro areas Portland and Seattle/tacoma is pretty smart on thier part...
http://www.r100.org/Schedule/default.aspx?p=2