The bedrock formed roughly 290 million years ago, deep underground, when a body of molten rock cooled slowly into the coarse-grained granite that geologists call the Bodmin Moor pluton. It is one of five such plutons in Cornwall, all part of the Cornubian batholith that runs the spine of the southwest peninsula. When the plug of granite intruded into older Devonian slates above it, the heat baked those slates into hornfels around the margins. Erosion eventually stripped away the overlying rock to expose the granite, and the freeze-thaw cycles of the Pleistocene shattered the surface into the boulder fields and tors that still define the moor. Brown Willy reaches 420 metres, the highest point in Cornwall. Rough Tor sits at 400 metres just to the northwest, and Kilmar Tor and Caradon Hill anchor the southeast. The peat that fills the hollows between these tors is much younger, Holocene in age, built up over the last 10,000 years by waterlogged plant remains that never quite decomposed.

Mesolithic hunter-gatherers wandered the area when it was still wooded, leaving flint scatters that show they sat down to knap blades on this hill or that hollow. By the Bronze Age the trees were retreating and the monument-building had begun. Over 300 cairns were raised across the moor, along with stone circles, stone rows, and the strange rectangular enclosure called King Arthur's Hall, east of St Breward, thought to be late Neolithic or early Bronze Age and serving some ceremonial purpose no one has reconstructed. In the late 1990s a team from UCL spent several seasons researching the Bronze Age landscapes of Leskernick, mapping how people had organized their lives across slopes that today look empty. Channel 4's Time Team excavated a 500-metre cairn and a Bronze Age village on the slopes of Rough Tor in 2007. Medieval times left their own mark: Foweymore, the moor's medieval name, became one of the four stannaries that administered tin mining under King John's 1201 charter, though the boundaries were never precisely defined.

Bodmin Moor is the parent watershed for much of Cornwall. The River Fowey rises at 290 metres elevation and flows down through Lostwithiel to the south coast. The Camel rises on Hendraburnick Down and runs forty kilometres before meeting the sea at Padstow. The Tiddy, the Lynher, the Inny, and the De Lank all originate on the moor's slopes. Three 20th-century reservoirs were built to capture this water for the growing population of the county: Colliford Lake, Siblyback Lake, and Crowdy Reservoir, between them supplying drinking water across most of Cornwall. The poor drainage that creates marshes in summer and bogs in winter has shaped the moor's biology as well as its hydrology. About 260 breeding pairs of European stonechats nest here, and around 10,000 Eurasian golden plovers winter on the open ground, prompting BirdLife International to designate the moor an Important Bird Area. 500 holdings still graze around 10,000 beef cattle, 55,000 breeding ewes, and a thousand semi-wild ponies.

Sightings of large black cats on Bodmin Moor have continued for decades, with grainy photographs and dead sheep periodically generating local panic and national headlines. The Beast of Bodmin is the most famous of the British big cat reports, and the evidence has consistently failed to live up to the story. When a skull retrieved from the River Fowey was presented to the Natural History Museum as physical proof, it turned out to have been cut from a leopard-skin rug. The real moor has darker stories that need no embellishment. In 1844 the body of 18-year-old Charlotte Dymond was discovered near Rough Tor; the labourer Matthew Weeks was tried, convicted, and hanged at Bodmin Gaol on 12 August of that year. A monument now marks the spot, and her grave lies in Davidstow churchyard. The 1988 Camelford water pollution incident, when twenty tonnes of aluminium sulphate were dumped into the public water supply at Lowermoor on the moor, would unfold into Britain's worst mass drinking-water poisoning and the long fight that followed.

Jamaica Inn stands beside the A30 where the road climbs over the moor at its highest point. Built in 1750 as a coaching inn, it served as a staging post for changing horses on the long haul between Launceston and Bodmin, and acquired a reputation for smuggling that Daphne du Maurier turned into a 1936 novel. The book made the place famous. Tourists now stop where smugglers once unloaded brandy. Other corners of the moor have stayed quieter. Robin Hanbury-Tenison farmed over 2,000 acres of Bodmin Moor hill country from 1960 to 2018, raising sheep, cattle, Angora goats, red deer, and wild boar imported from Russia, and eventually farming energy from wind, solar, water, and biomass on the same ground. His son Merlin took over in 2018 with a focus on sustainability. The moor still does what it has always done: support whoever can read its weather, its peat, its short summer light, and its long granite memory.