The Nataqua Territory was a short lived and unofficial territory of the United States. It consisted of a portion of what is now northeastern California and northwestern Nevada, centered on Susanville, California. In 1856, the border between California and the Utah Territory was unsurveyed and poorly defined. Local residents took advantage of this ambiguity and justified their resistance to tax collectors from Plumas County, California, by proclaiming themselves part of the Nataqua Territory. The Susanville convention which announced the Nataqua Territory went on to define a rectangle shaped territory by latitude and longitude which technically did not include their own Honey Lake Valley, but did encompass most of what soon became western Nevada. The independence movement was led by Peter Lassen and Isaac Roop. Association with the Utah Territory was unpalatable to the residents due to anti-Mormonism. The first governor of the territory was Lassen, followed by Roop in 1859 (after Lassen's death).
Subsequent to the formation of the Nevada Territory in 1861, Roop County, Nevada, was formed encompassing the area of the Nataqua Territory, and the pretense of independence was dropped. In 1863 a border survey found Susanville and virtually all the population of Roop County was actually in California. The California portion of Roop County became Lassen County, California in 1864.
- Davis, William Newell, Jr. (September 1942). "The Territory of Nataqua: an Episode in Pioneer Government East of the Sierra". California Historical Society Quarterly 1 (3): 225–28.
- "US 395: Lassen County (Susanville to Modoc County Line)". Floodgap Roadgap. Retrieved 2006-04-01.