- Total 2,613 sq mi (6,770 km2)
- Land 2,553 sq mi (6,610 km2)
- Water 60 sq mi (200 km2)
Population (April 1, 2010)
- Total 20,007
- Estimate (2016) 18,627
- Density 7.7/sq mi (3.0/km2)
Prior to the California Gold Rush of 1849, the indigenous Mountain Maidu were the primary inhabitants of the area now known as Plumas County. The Maidu lived in small settlements along the edges of valleys, subsisting on roots, acorns, grasses, seeds, and occasionally fish and big game. They were decentralized and had no tribal leadership; most bands lived along waterways in and around their own valleys. Areas with high snowfall, including the Mohawk and Sierra valleys, were hunting grounds for game in the warmer months.
In 1848, European Americans discovered gold in the Sierra foothills. Miners were attracted to Plumas County in particular, largely due to the tales of Thomas Stoddard, who claimed to have discovered a lake lined with gold nuggets while lost in the wilderness. Gold-hungry prospectors flooded into the area. Though hopeful miners scoured the glacial lakes (now designated as the Lakes Basin Recreation Area) for months, they did not find the purported lake of gold.
But some had success panning for gold in the rivers and creeks in the area, and created squatters’ villages, the first non-Native American settlements.
Rough shanty towns quickly sprang up around successful mining areas, including Rich Bar, Indian Bar, and Rabbit Creek (now La Porte). Many were developed adjacent to the Feather River, named by Spanish explorer Captain Luis Arguello as Río de las Plumas in 1820.
In 1850 notable African-American frontiersman James Beckwourth discovered the lowest pass through the Sierras, which became known as Beckwourth Pass. Using the pass, he blazed a trail that began in Western Nevada and went through much of Plumas County, eventually terminating in the Sacramento Valley. This trail was followed by many erstwhile miners into Plumas County. Beckwourth also set up a trading post in the western Sierra Valley that still stands today. Though the Beckwourth Trail was longer than the original emigrant trail that ran south of Plumas County, its lower elevations extended its seasonal use when the higher trail was snowbound and impassable. The Beckwourth Trail had heavy use until about 1865, after construction of the transcontinental railroad, when railroads became the favored transportation method for westward-bound travelers.
Plumas County was formed in 1854 during a meeting of three commissioners held at the American Ranch in Quincy. It was carved from the eastern portion of Butte County. Quincy, originally a mining town, was chosen as the county seat after an early settler donated a plot of land there to establish the seat. Once it became the seat, nearby Elizabethtown faded and ultimately became defunct. In 1864, the state legislature took a large portion of Plumas County to organize Lassen County because of increasing population. Shortly afterward Plumas County annexed part of Sierra County, including the prosperous mining town of La Porte.
Over the next decades, different industries drove the growth of the various settlements that sprung up around the county. Greenville began as a mining and farming community in Indian Valley in the late 1850s. Chester was formed near the area that is now Lake Almanor, as a result of cattle ranching and the timber industry.
When the Western Pacific Railroad was constructed in 1910, Portola developed as an important railroad stop. Thanks to the railroad, Plumas County could export its lumber beyond the local area, and the timber industry became dominant in the county’s economy for decades. As the railroad route extended up the Feather River Canyon, it was also used by the area’s first tourists and sightseers. When the Feather River Highway was completed in 1937, through federal investment in infrastructure by President Franklin D. Roosevelt during the Great Depression, Plumas County became linked to the Sacramento Valley year-round thanks to the route’s low elevation.