Alley Spring's cold, clear water churns from a funnel-shaped basin at an average flow of 81 million gallons per day, and its abundant fresh water has drawn people there for centuries, from native peoples indicated by archeological evidence to early settlers who built a grist mill at the spring's edge about 1868. In 1894 a steel roller mill was constructed on the same site and still stands, with steel rollers powered by a turbine rather than a waterwheel; the turbine can be seen beneath the porch on the east side of the mill. The mill's presence led to additional services, and after a post office was designated in 1884 the area became known as Alley. The community that grew around the mill eventually included a general store, blacksmith shop, and school. Because of early preservation efforts, Alley Spring Mill remains a symbol of heritage. In 1924 Alley Spring became a Missouri state park, and in 1964 the State of Missouri gave it to the National Park Service as part of the Ozark National Scenic Riverways.