Badlands National Park protects one of the most geologically dramatic and visually unusual landscapes on the continent — a vast expanse of sharply eroded buttes, pinnacles, and spires rising from the mixed-grass prairie of southwestern South Dakota, layered in banded sediment that reads like a compressed geological library. The Lakota people who first named this place called it mak̄hóšiča — "bad lands" — for its extreme heat, scarce water, and nearly impassable terrain. French trappers echoed the sentiment with les mauvaises terres à traverser — "bad lands to travel through." For photographers, it is among the most extraordinary landscapes in North America.

The geology is the story. Beginning roughly 75 million years ago, when a vast inland sea covered this region, sediments began stacking in horizontal layers — shale from the sea floor, then river deposits, volcanic ash, and windblown silts — accumulating over tens of millions of years into a geological layer cake hundreds of feet deep. Erosion by the Cheyenne, White, and Bad River systems began carving into these layers approximately 500,000 years ago — a geologic eyeblink — and continues today at a rate of roughly one inch per year. The different layers erode at different rates, producing the steeply undercut pinnacles, the mushroom-capped hoodoos, and the smoothly striated butte walls that define the Badlands landscape. At this rate, geologists estimate the formations will be completely gone in another half million years.

Embedded in those layers is the world's richest known fossil record from the Oligocene epoch — 23 to 35 million years ago, the "Golden Age of Mammals." Ancient three-toed horses, hornless rhinoceroses, saber-toothed cats, tiny deer-like creatures, and early camels all lived here and died here and are still being found here by paleontologists who return every summer season. The park's 244,000 acres also protect the largest expanse of mixed-grass prairie under federal protection, where today's bison, bighorn sheep, pronghorn, prairie dogs, and the reintroduced black-footed ferret carry on in the landscape their ancient relatives once shared.