I've driven from San Francisco to Seattle in a day - a very, very long day. The distance between the 2 cities is about 800 miles. So you can expect the total drive time to be about 13 hours, not including rest stops. So I'd allow 2 days for the drive.
Of course if you have extra time, there are some fabulous sights along the way!
If you take Interstate 5, you will pass Mount Shasta. This is a beautiful snow capped mountain with a Lake that's a popular recreation spot.
I-5 will take you through Ashland, Oregon. Ashland is famous for it's Shakespeare festival that is held every summer. They have a beautiful Elizabethan outdoor theatre.
You can detour off of the interstate to visit Crater Lake National Park in Oregon. http://www.nps.gov/crla/ I have not been to this park yet. But it looks absolutely amazing.
I-5 will take you through Portland, Oregon's largest city. Portland offers some good shopping opportunities. Oregon State has no sales tax. So if you plan to do shopping, it's better to do it there than in California or Washington.
When you enter Washington, you can detour to see Mount Saint Helens http://www.fs.fed.us/gpnf/mshnvm/ and Mount Rainier National Park. http://www.nps.gov/mora/
** Even in June, some of our mountains have restricted access due to snow. So if you plan to visit Rainier or Crater Lake, check to see if any areas of the park are closed before you go. And be prepared to possibly even have to leave the park early due to a snow storm. It happened to me once during a visit to Rainier in June!
Another option is to take Highway 101 from San Francisco. This highway will take you closer to the coast. In California, 101 passes through the Humboldt Redwoods State Park http://www.humboldtredwoods.org/ and the Redwoods National Park. http://www.nps.gov/redw/ The Avenue of the Giants is a short scenic drive in the Humboldt that should not be missed. http://avenueofthegiants.net/ This is where you can easily get into the middle of some truly amazing trees.
In Oregon 101 will take you along the coast. This stretch of the Pacific Coast is known for it's rugged beauty. The area is dotted with small towns.
Be aware that 101 is a slower road to drive than I-5. So if you plan to drive any sizable stretch of it, allow for extra time. There are several small highways that connect 101 and I-5, so you can easily cross between the two to catch the sights that are most interesting to you.
You mentioned camping. The National Parks all have several campgrounds. Some are RV, some are tent some are both. Some take reservations, some are first come first serve. Some are closed during snow months due to elevation. You can find information on all of them on the NPS sites above.
If you want to camp outside of the parks, I recommend looking at KOA. Kampgrounds of America is a national chain. The good thing about them is they are easy to find and you know what you'll get. www.koa.com
A lot of campgrounds are privately owned, in State Parks or on other Government own land. The private ones can be a bit tougher to find in advance. If you think you will be stopping in a state park or other Government property, you should be able to easily search for the area to find a campground. For example, the State Park site for the Humbodlt Redwoods above, does list camping information as well.
Hope this helps! Have a great trip!
(¸. Michelle ¸.·
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