Prior to the California Gold Rush, the area was home to both the Maidu and the Washoe peoples.

Most mining settlements in the county sprung up along the North and Middle Forks of the Yuba River, both of which had rich deposits of gold.

While some of the mining boom towns faded away once gold fever died down, other settlements such as Downieville and Sierra City have remained.

[9] The Bald Mountain drift mine in Forest City was founded in Aug. 1864, and was the largest of its kind in the state at the time.

In particular, the statute, at the time codified as Section 3921 of the California Political Code, at the time stated: ...thence south on said state line (state of Nevada) to the northeast corner of Nevada County, a point east of the source of the South Fork of the Middle Yuba River; thence west to the source of, and down the South Fork of the Middle Yuba River to a point ten miles above the mouth of the latter.Since the line was not surveyed and the legislature never defined where the "point east of the source of the South Fork of the Middle Yuba River" was, the location of the straight air line between the state line and this point was unknown.

It also determined that the source of South Fork of the Middle Yuba River was that of several springs in the Sierra Nevada, contrary to the artificial English Lake, which ceased to exist after the failure of its dam in 1883, which is where the source of said waterway was in the eyes of Nevada County.

The county has a diverse range of landscapes, from mountains to forests, with numerous lakes and streams.

Due to the county's sparse population and geographical obstacles, the Sheriff's Department operates a substation in Loyalton in addition to their main headquarters in Downieville.

On November 4, 2008, Sierra County voted 64.2% for Proposition 8, which amended the California Constitution to ban same-sex marriages.

[19] There is only one traffic signal (a flashing red light at the intersection of highways 49 and 89) in Sierra County.

The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.

This paper has been published bi-weekly since 1949 when it was established by reporter, miner, and airman Hal Wright and his wife Allene.

The Messenger has been in constant publication since 1853 and is currently the longest-running weekly newspaper in the state of California.

Its more notable former contributor was Mark Twain, at the time in hiding from Nevadan authorities and writing under his birth name of Samuel Clemens.

[42] This paper was the center of considerable media attention in early 2020 when its future was uncertain with the retirement of Don Russell, who had owned and operated it for 30 years; it was saved by local retiree Carl Butz, who purchased the paper and runs it today.

[43][44] The Mountain Messenger is printed every Thursday by Feather Publishing Co., based in Quincy; it is distributed across Sierra, eastern Plumas and western Nevada counties.