You didn’t say if you’re doing a round-trip or a one-way drive so I’ll assume that you’re going one-way. I’ll also assume that you’ve been to Olympic and Mt Rainier National Parks since they’re both within a half-day drive of Seattle.

Traveling south from Seattle on I-5, my first stop would be Mt. Saint Helens Volcanic National Monument. I’m always impressed by the raw power of mother nature and Mt. Saint Helens is a good example of that. Continuing south, go east at Portland and drive the Historic Columbia River Highway. Be sure to stop at Multnomah Falls near the eastern end of the drive. Continue east following the Columbia River. Stop to see the Bonneville Dam and the wind surfers near Hood River. At Hood River, turn south on 35 and continue south on 26/97 to get to Crater Lake National Park, a must see. The lake is the most beautiful color of blue you will ever see. Take the 33 mile drive around the lake and consider the one mile walk into the crater to get to the lake.

If your plan is to see Redwoods National Park then from Crater Lake turn westward on 62/234/I-5 and head for Grants Pass. At Grants Pass turn southwest on 199 and go to Cave Junction then turn east on 46 to get to Oregon Caves National Monument. From there you can return to Cave Junction and turn south on 199/101 to get to Redwood National Park. Redwood NP may not be what you’re expecting. This park is more of a hiker’s park and access to the coastline is primarily by trail or 4-wheel drive vehicles. Stop at the Prairie Creek and Kuchel Visitor Centers. Look for elk at Elk Prairie and Elk Meadow. The tallest trees in the park are located in the southern region of the park and is accessible by dirt road and trail only (permit required). Patrick’s Point State Park located south of the NP on 101 is a nice place to stop and take a short walk down to the coastline. An easier way to see tall trees is by driving the Avenue of the Giants located south of Eureka between Elinor and Phillipsville. Humboldt Redwoods State Park is another good place to see tall trees.

Instead of Redwoods National Park, I recommend that you continue driving south from Crater Lake on 62/97/39/139 to Tule Lake and Lava Beds National Monument. This park is full of lava tubes that you can walk through but wear sturdy shoes and watch your head if you do. The lava in some places is razor sharp and will split your scalp open if you forget to duck. Continue south on 139/299 until you get to 89 then go north a little ways to get to McArthur-Burney Falls Memorial State Park to see the falls. From there continue south on 89 to get to Lassen Volcanic National Park. Exiting through Lassen’s south entrance station turn west to get to the town of Red Bluff. From there go south on I-5 until you get to Sacramento then switch to 99 and continue south until you reach Merced. Go east on 140 and enter Yosemite through the west entrance. Be sure to see the Mariposa Grove of Giant Sequoias near the south entrance. Sequoia trees are the world’s largest trees. They are not the tallest although they can grow to more than 300 feet tall. The coastal redwoods of Redwoods National Park are the tallest in the world while the giant sequoias are the largest volume wise. The General Sherman Tree in Sequoia National Park is 275 feet tall which is a full 100 feet shorter than the world’s tallest tree but has a circumference of 102 feet. The diameter of it’s largest branch is 7 feet – that’s larger than many trees. If you want to see this massive tree and the General Grant (2nd largest in the world), leave Yosemite through the south entrance and go to Fresno then turn east on 180 which will take you into Sequoia National Park.

To get to San Francisco, go west from Yosemite or Sequoia to get to 99 then go north to Manteca. At Manteca go west on 120/205/580. You can also go west on 152 from 99 south of Merced and north of Madera. 152 west will take you to Gilroy then go north on 101 to get to San Jose.

Enjoy your road-trip.