Observation Peak is located in northeastern California, north of Susanville. Observation Peak is a rough drive up to a fire lookout. The access is has several miles of rocky access road that mandates a very slow approach. High Clearance is recommended for access, but any truck should be able to negotiate the road.
There is a manned fire lookout on the summit and the guy was very welcoming. He told me the entire mountain burned over a few years ago. 6/22/2006
As the beta on the page says, I would agree with the statement that "any truck should be able to negotiate the road", but what's the point? The road is about 6 miles long, and is in such poor shape (as of 10/2010) that your average speed will be about 3-4mph. Most SPers in decent shape can walk faster than that. I have a 4WD Jeep Wrangler (and know how to drive it), and it took nearly 2h to go up and back down from Horn road.