Devils Tower, known as Bear's Lodge to Northern Plains Tribes, rises high above the Belle Fourche River, grasslands, and ponderosa pine forests. This major landmark of the Northern Great Plains has attracted people for thousands of years. Today, it still holds many meanings for people including American Indians, local ranchers, rock climbers and thousands of visitors from near and far.
The Tower and the Missouri Buttes to the northwest formed about 50 million years ago. They are the result of magma (molten rock) being forced up from below the earth's crust. Following cracks and weak spots, the molten rock moved up and pooled beneath the land surface. There the magma cooled and hardened. As it cooled, the rock shrank and cracked. Those cracks made the 4, 5, 6 and 7-sided columns we see today. Over time, ancient rivers washed away about 1.5 miles of the softer sedimentary rock layers that covered the Tower. Erosion is still slowly wearing away the hard igneous rock of Devils Tower.
There are many columnar rock features in the world. The Tower is unique because of its size and type of rock (phonolite). The columns that create Devils Tower are the tallest (some more than 600 feet) and the widest (10-20 feet in diameter). Some geologists estimate the last rock column fell 10,000 years ago.