The Iroquois Confederacy claimed these mountains as a hunting ground - by right, the Confederacy said, of their conquest of earlier nations who had lived here. A British treaty of 1758 confirmed the land west of the Allegheny Mountains to the Native nations and forbade the Crown's subjects from settling or hunting in it. The treaty did not hold. British settlers kept moving in, and the Native nations defended their hunting grounds in raids and counter-raids that filled the next two decades. After the American Revolution, the Native nations migrated west under pressure that ranged from negotiation to outright displacement, and settler claims were regularized into the county system that exists today. The county was established in 1821, while the region was still part of Virginia, and named for Pocahontas - the Powhatan woman who, more than two centuries earlier, had married John Rolfe at Jamestown and through whom many of the First Families of Virginia traced their descent.

When the Civil War came, Pocahontas County voted to secede from the United States by 360 to 13. About 700 of the county's 907 men of military age served in the Confederate army. The county levied $15,000 for armaments. Farming became difficult as men left for the front, and many of the county's 252 enslaved people fled during Union troop movements through the valleys. Some local Unionists who had escaped to Upshur County to the north enlisted in the 10th West Virginia Infantry Regiment. Three Civil War engagements took place on the county's mountain ground: the Battle of Cheat Mountain and the Battle of Camp Allegheny, both in 1861, and the Battle of Droop Mountain in 1863 - the last a Union victory that broke Confederate control of the area. When West Virginia was carved out of Virginia in 1863, Pocahontas County was added to the new state without its citizens' input. Voting rights for most of the county's adults, who had supported Richmond, were not fully restored until 1871.

The railroads came late to Pocahontas County. Building track over the Alleghenies was difficult and expensive enough that construction did not begin until 1899. Once the line was in, the change was startling. The Chesapeake and Ohio Railway opened the great virgin forests of the high mountains to commercial timbering. The West Virginia Pulp and Paper Company built a massive mill at Cass that became the center of a company town. By the end of 1920, dozens of small railroading and lumber towns dotted the county. European immigrants - many of whom had built the railroad itself - settled into mill jobs. The 1900 census shows the rapid demographic shift. The boom was brief. By the 1930s, the great forests had been mostly cut, and the lumber towns began to empty out one by one. The Monongahela National Forest, established in 1920, eventually grew to protect what was left and to manage the watershed regeneration.

The county sits at the crown of the central Appalachians. Its mean altitude of 3,219 feet makes it the sixth-highest county east of the Mississippi River and the highest in the eastern U.S. outside western North Carolina. Eight rivers begin in Pocahontas County: the Cherry, Cranberry, Elk, Gauley, Greenbrier, Tygart Valley, Williams, and the Shavers Fork of the Cheat River. Some flow west, eventually joining the Ohio River and reaching the Gulf of Mexico via the Mississippi. Others flow east, joining the Potomac and the Atlantic. The high point is Thorny Flat on Cheat Mountain at 4,848 feet. The Monongahela National Forest protects much of the river headwaters, the Cranberry Glades Botanical Area preserves a glacial-relict bog system, and the Gaudineer Scenic Area shelters one of the eastern United States' few stands of virgin red spruce.

Today the county's most unusual claim to fame is its silence. Pocahontas County is the heart of the United States National Radio Quiet Zone, a 13,000-square-mile area centered on the Green Bank Observatory where radio emissions are heavily restricted to protect the world's largest fully steerable radio telescope. Cell phone service is essentially nonexistent. Wi-Fi is limited. Drivers from outside the area sometimes panic when their phones lose signal coming up US-219. Permanent residents have adapted to a life with less constant electronic noise than almost anywhere else in the continental United States - a small social experiment running quietly in the same county where European settlement once meant a man living in a hollow tree.