Spearfish Canyon is a State and National Forest Scenic Byway that winds for 20 miles along Spearfish Creek between the communities of Spearfish  and Lead . The byway is U.S. 14A and is also a commercial highway, so be sure to pull well off the road when stopping to view the scenery. All of the views are straight up the canyon walls to heights of over 1,000 feet, but don’t forget to keep an eye on the road as many bicyclists and hikers may be riding or walking along the highway shoulders.
Over two billion years ago, the area that is now the Black Hills  was covered by an inland sea. Over time, as the sea receded and returned and receded again, layers of sediment were deposited on the ocean floor. As these layers hardened, different sedimentary layers were created. Around 65 million years ago, a dome-shaped uplift in the earth’s crust formed the Black Hills.
In the Northern Hills , crevasses within the limestone layer, created by the uplift, filled with magma. These magma flows, called intrusions, cooled forming igneous rocks. Limestone and other sedimentary layers erode faster than the harder igneous rock, so while the sea receded, the overlying sedimentary layers were eroded, exposing the igneous intrusions.
Crow Peak, Spearfish Mountain, and Terry Peak in the Spearfish area are all igneous intrusions, as is Bear Butte, the easternmost igneous peak in the region.
About five million years ago, the erosion of the limestone layer near Spearfish  was accelerated by the power of water. Many of the streams that flow out of the hills begin as springs within the limestone plateau on the western side of the hills. Spearfish Creek is one of those streams. Today, the streambed of Spearfish Canyon is more than 1,000 feet below the highest canyon walls.
The river runs from south to north and passes through four different plant communities on its way. Northern Coniferous Forest, featuring white spruce trees, merges into the dominant biome of the region, the Rocky Mountain Pine Forest, which includes the ponderosa pine and which covers 85 percent of the Black Hills region. Next, the Eastern Deciduous Forest makes inroads into the hills with stands of quaking aspen and birch. As the creek spills into the Spearfish river valley, the northern plains habitat of oak and cottonwood trees, and prairie grasses appears. Of the 1,585 plant species found in the state of South Dakota, 1,260 are found in the Black Hills , and most of these can be found in Spearfish Canyon.
When the communities of Spearfish  and Lead  were founded in 1876, the canyon between the two communities was impassable, even on horseback. It wasn’t until 1893 that the Grand Island and Wyoming Line Railroad built a direct rail line through the canyon terminating at the Homestake Mine in Lead  that beautiful Spearfish Canyon became accessible for day trips. Visitors to the canyon could ride the train to any point they wished and the train would stop and pick them up on the return trip.
Begin the drive from Spearfish. Take exit 10 or exit 14 off of I-90 and follow the signs to the Spearfish Canyon Highway. At the intersection of U.S. 14 and U.S. 14A (the scenic byway), head south. The National Forest Service has created a self-guided tour brochure that is available at the Spearfish Ranger District office (2014 N. Main St., Spearfish, 605/642-4622).