Northeast of Medford near Chiloquin, the Williamson River starts in the springs near Klamath Marsh and heads southwest through Chiloquin to Upper Klamath Lake. This 75 mile river is known for its huge rainbow trout, many of which are over 18 inches long. But these monsters are smart and can be difficult to land. Look for the red band rainbows which can be landed with nymphs.
The best section for fly fishing on the Williamson River is from the public launch site upstream of Water Wheel Campground back down to the campground. Since the river flows through a great deal of private property, you may want to try floating this one.
Overall, Williamson River is the 11th most popular fly fishing river of all 22 fly fishing spots in Oregon.