Alley Spring, the natural area’s namesake, is the seventh-largest spring in Missouri. The spring conduit is known to extend at least 3000 feet underground and reach at least 155 feet below the surface.
Just an hour west of downtown St. Louis is a different world that seems far removed from the city. These hills forming the watershed of LaBarque Creek conserve a wide variety of aquatic and terrestrial life.
This scenic natural area contains all sorts of fascinating sandstone rock formations including box canyons and wet weather waterfalls. The sandstone rock here is the Lamotte sandstone that was formed from sandy beaches of a shallow ocean that existed here 500 million years ago.
About 250 million years ago Boone County was covered by a shallow sea. This sea teemed with life and the fossilized remains of these ancient sea creatures are preserved in the Burlington limestone bedrock that composes the “Pinnacles” rock formations here.