The bright-red mill and turquoise spring that put the Jacks Fork on every postcard.
Alley Spring, the natural area's namesake, is the seventh largest spring in Missouri. Its conduit is known to extend at least 3,000 feet underground and reaches at least 155 feet below the surface, fed by rainfall and runoff entering sinkholes across the surrounding landscape.
The red Alley Mill, built in 1894, is one of the most recognizable historic structures in the state. In summer, the mill is open for tours; year-round it's the visual centerpiece of the Alley Spring area and a favorite of photographers.