Lassen County is a county located in the northeastern portion of the U.S. state of California. As of the 2010 census, the population was 34,895, up from 33,828 at the 2000 census. The county seat is Susanville, the only incorporated city in the county.
Lassen County was formed on April 1, 1864 from parts of Plumas and Shasta Counties following the two-day conflict known as the "Sagebrush War", also called the Roop County War, that started on February 15, 1863. Due to uncertainties over the California border, the area that is now Lassen County was part of the unofficial Nataqua Territory and Roop County, Nevada during the late 1850s and early 1860s.
The county was named after Peter Lassen, along with Lassen Peak, which is in adjoining Shasta County. Lassen was one of General John C. Fremont's guides, and a famous trapper, frontiersman and Indian fighter. He was murdered under mysterious circumstances near the Black Rock Desert in 1859, and his murder was never solved.
By the 1880s small towns began to spring up all over Lassen County. Bieber was at the north end of the county, in rich farm land. Hayden Hill was where a gold discovery happened, and a small town sprang up to support the miners. Hayden Hill no longer exists: as the mining stopped, the town's people left for other communities. Madeline was formed at the north end of another rich farming valley, and along the railroad tracks heading north to Alturas, California, this community to this day has about 50 people living in and around the town. A narrow gauge railroad ran through Lassen County from 1880 to 1927, and was called the Nevada-California-Oregon Railway. The N.C.O.R. was the longest small gauge of the century. It was meant to connect Reno, Nevada to the Columbia River, but only of track were laid, from Reno to Lakeview, Oregon.
In 1913 the Fernley & Lassen Railroad was built and would tap the large timber supplies of Lassen County. Along with this railroad being built, along came the Red River Lumber Company, who built the town of Westwood, California to support their massive logging operation. Two other lumber mills followed the Red River Lumber Co. They built their mills in Susanville, California. The Lassen Lumber & Box Company and the Fruit Growers Company both operated mills in Susanville for several decades.
In May 2007, Sierra Pacific Industries, based in Redding, California, closed the last lumber mill in Susanville, due to the lack of large timber for the mill. The mill was a large-timber mill, and would have required several million dollars to convert it to small timber. Sierra Pacific was reluctant to invest in the mill, and elected to close it permanently.