Actually, though I've been through the gorge many times, I'm not sure if this would be on the east or west of The Dalles, OR, but I know it is east of the Cascade mountain range the gorge cuts through east of Portland.
It is a most interesting place though, due to the extreme contrast between the Oregon side on the right in the painting, and the soft hills of southern central Washington state on the left.
I'm not sure if I am finished with this. The plant in the foreground seems to be begging for assistance.
The original sketch for this 14x18 painting is posted below at Sketchbook Project #11.