Do I dare say this river is the most scenic and fun Class IV rafting trip in California? No, because you are very likely to freeze your but off. This trip is normally done during or soon after rainstorms in February or March.
The North Fork of the Smith begins in Oregon and the normal put-in for this run is just downriver of the Oregon border. You'll enjoy a fairly long and very scenic (unless it's raining) drive to put-in at Major Moore's where you'll get a sense of the remote wilderness you're in. You'll immediately be awestruck by the clarity and greenish color of the water.
This run starts off with some great warm up rapids. After Diamond Creek enters on the left side, start paying attention for the rapids to pick up. The Redwood Gorge starts around mile four with a number of great Class III and IV rapids. The rest of the run is scattered with Class III and IV rapids.
There are several spectacular stops on the North Fork at great waterfalls and side creeks. At most of these stops, you'll have a chance to check out the California Pitcher Plant. This is a rare carnivorous plant that uses ultraviolet guides and slippery wax to lure insects and spiders into it's inner workings.
You're a lucky one if you get a chance to do the North Fork of the Smith. Just remember to bring plenty of warm boating gear and a thermos full of hot chocolate.