The farthest upstream launch that I know of is at Borst Park, If your interested in the lower Chehalis there are several on this stretch. One on the Black River (outside Oakville on Hyw. 12, one below Oakville on the Chehalis, One at Porter, one at Keys Rd. (above the mouth of the Satsop), one at Montesano, Freinds landing, and Cosmopolis. These are all useable launches BUT it depends on what you are going to be on the water in (type of craft, there are a lot of sweepers and the current can get you in trouble if you are not prepared, there are also riffles that can be shallow, right now most of the riffles should have enough water to navagate. I hope this may have helped.