Just south of Eureka - Loleta Cheese Factory small cheese company, makes a variety of cheeses right behind the big windows in the sales room. The sales room has samples, lots and lots of samples. Even if you don't particularly care for cheese, you'll find something you like.
http://www.destinationtba.com/2014/05/09/loleta-california/
Ferndale - a small town built mostly at the height of the lumber industry and with all the mills and mill works around, they went the limit. About a square mile packed with Victorian Buildings and houses, almost all painted authentically.
Eureka -
Samoa Cookhouse - Just over the bridge from Eureka, formerly the cookhouse in a logging company mill town. Basically served family style, usually just a few entrees, veggies, soup, salad, made and served just like it was in the old days. Just down the road is the former navy airship station, the location of some coast defense guns, mostly AA and the Coast Guard Lifeboat Station (drive down there, too, to settle your dinner)
Ft. Humboldt State Park, display of old logging equipment, and home of a few operating dinky steam engines
Blue Ox Millworks - tours of original millworks including man-powered saws, lathes, milllworking machinery, Able to make just about anything for building houses, buildings, decorations, etc made of wood. They source millworks to restorations, artists, museums, new construction all over the world. Want to see how they made pickets for picket fences all the same size and shape, they show you. If there is even a hint of craftsman in you, this stop is required.
Take a tour of the downtown area, crammed with ornate Victorian buildings, but larger than Ferndale, Eureka was the big city then and now and the larger buildings in the business district reflect it. Also a lot of Victorian houses.
If you continue north along the coast, Prairie Creek Redwoods State Park, go out to Gold Bluffs Beach and Fern Canyon. The Canyon hike is about a hundred yards or so from the parking lot and then roughly a mile through this small canyon varying for maybe 20 fett to 40 yds wide, the walls are covered with several kinds of ferns, you walk along the creek bed, mostly on dry gravel portions of the bottom, but there are some fallen logs you need to climb over or walk along to cross the creek and there are a few foot bridges.