You can -but if you want to is the question. Sticking to 101, SF to Crescent City takes about 7 hours w/o any stops.

Crescent city to Portland via I-5 takes about the same. So when factoring in photo stops, meals, rest breaks you are basically driving ALL day both days.

(continuing on to Seattle is even worse - Crescent City to Seattle takes about 10 hours 'car time')

to go thru Ft. Bragg on way to Crescent City would consume extra 2 hrs as Ft. Bragg is not on 101...it is not so much the actual miles but all 2 lane roads, often very twisty..
I 5--in winter can be very iffy as to "snow-chains" from Shasta area and around Ashland Oregon.
Going up Oregon coast from Crescent City would seem logical way to avoid "weather' problems...However, the coastal highway, while beautiful, is very slow going..averaging 40-55 MPH. You could consider going 1/2 way upcoast and then cut over to I 5 into Eugene or Salem.
Good Luck

In March it will be dark by the time you hit the Oregon border using US 101 and Calif. SR 1. Plus, the best views of the Redwoods are on the (very slow) portion of US 101 between Arcata (north of Eureka) and Crescent City. Plus plus, in March it will almost certainly be rainy for some portion (could be a large portion) of the drive up the coast, which will further restrict speed and visibility.

I can't see making this trip without an overnight stop someplace, maybe two depending on conditions. Perhaps you could indicate how much time you have for the drive altogether.

Good advice above. My plan for what it's worth: Stay on US101 from San Francisco to Klamath 6.3 hours (335 mi). Stay at the Ravenwood Motel. Get up early the next morning and stop a couple miles up the road at "The Trees of Mystery" for no more than 2 hours. Continue up 101 to Crescent City where you get on US 199. You will also see some big Coast Redwoods along 199 even over the border into Oregon. You will hit I-5 near Grants Pass Oregon. From Klamath to Portland is 6.3 hours (348 mi.).
From Portland to Seattle is 3.0 hours (174 mi.).
If you find that you can spend another night continue up the Oregon coast and stay in Newport and spend a couple hours at the Oregon Coast Aquarium and then heading east on US 20 to get on I-5 at Albany Oregon.

Thank everyone - it is extremely helpful. I didn't even consider weather patterns. I plan to leave San Fran on a Thursday and was hoping to be in Seattle by Friday but maybe if I try to get to Seattle by Saturday sounds more reasonable (planning to stay overnight 2 nights on the road). Great advice and much appreciated

You are right that it would be better to spend two nights on the road.

For the Redwoods and great ocean views, I would drive Highway 101 to the Redwoods and spend the night in Brookings, OR. From Brookings, I would drive 101 to Cannon Beach and spend the night there (314 miles/8 hours).

If I wanted to make the trip with one night on the road, I would drive from Brookings to Reedsport (great ocean views as far as Port Orford and fast food in Coos Bay), drive to I-5 on Highway 38 (which follows the beautiful Umpqual River) and then I-5 to Seattle (502 miles/9 1/2 hours).

HTtY

Look here for lodging IN the redwoods along the Avenue of the Giants: avenueofthegiants.net/motels_inns.html.

If you don't like hoopla, don't stay at the Benbow Inn.

Hey, bobmrg - I just looked at the Bendow Inn. I do see that it is more "upscale" and has a dress code for the dining room. Is that what you are referring to?

Just trying to put it in my notes, as am planning a vacation that will include this area and want to understand that underlying feeling that one encounters (for better or worse). If my impression is correct, that may or may not be what I'm looking for.

I love LOVE the Benbow. Not sure what the 'hoopla' comment is about.

There is hardly what I would call an onerous 'dress code' - if one wants to be more casual than (from the website) >>For dinner: polo-type shirt, Dockers, slacks and nice jeans are perfectly acceptable. We do ask that no sandals, shorts, bathing suits or bare feet find their way into the dining room,<< . . . then no, the Benbow is not for them.

But if you want the feeling of an English country inn and pub, it fills the bill.