This section of Hwy 89 goes right through Lassen National Park. Yes, you have to pay $5 for passing through. But it's definitely worthwhile.
You start at the intersection with Hwy 36 and you begon to clim right away. In fact, you keep climbing for the next 20 km and gain about 850 m in the process. That's an average grade of just over 4% and you have many excuses for taking breaks: take pictures, look at the hot springs, etc.
Once you are over the top, you can enjoy a log descent with views towards the North and East and back to Lassen Peak. You have a shorter climb before you reach the park gates on the Northern end.
Southern Approach
Waterfall (before the entrance gate)
Sulphur Works
Mt Diller
Mt Conard
Diamond Peak
Looking South
Pilot Pinnacle
Ski Heil Peak
At the Top
Almost there - just working your way through the snow
Looking back over Lake Helen
Lassen Peak close up
View to the North-East from the top
Northern Approach
Lassen Peak
Lassen Peak
This is about a kilometer from the pass
Manzanita Lake