To summarize, a large portion of the part of California north of Lake Tahoe and east of the Sierra Nevada range was formed as Plumas County, CA. Later, someone goofed and granted Nevada an overlapping claim to the same land. Nevada formed Roop County in that area and the citizens of the area were divided over their loyalties.
Plumas County courts and tax officials tried to exert control. Roop County courts also tried to exert control. The competing courts issued arrest warrants for the offenders on each side. The governors of each state stood their ground. A citizens’ skirmish ensued with gunfire on 2/15/1863.
Later, a survey settled the matter, and the area was considered part of Plumas County, California. However, the pro-Nevada rebels, led by Peter Lassen, were pissed about the whole thing and formed Lassen County, CA by splitting from Plumas County on 4/1/1864.
Not quite true. A very detailed summation can be found at Wikipedia: Toledo War. There was one person stabbed, by famously named “Two Stickney.”
Also, the jurisdiction of the SCotUS to adjudicate state boundary claims wasn’t originally considered to be well established. I’ll chime in later with the case that was definitive.