Susanville, CA is the county seat of Lassen County. Emigrant trails leading west to the gold fields were established in this area in the 1850's. Going through Donner's Pass was very difficult, and the journey through the Honey Lake Valley was easier. The emigrant trails took pioneers to Shasta City on the northern top of the Sacramento Valley.
The first residents of Lassen County tried unsuccessfully to declare themselves a separate Republic. The US Government didn't allow that. To read more about the beginning of Lassen County, visit the Lassen County Historian's site:
This photo is the monument to Peter Lassen. He was one of the first settlers in the Honey Lake Valley/Susanville area. More information about his life can be found by clicking on the above link. He was a pretty interesting man.