According to the sign at the top of the hill,
"in 1918, a flood destroyed an existing wood dam at Freeman’s Mill. Newt G. Phan, who owned several county gristmills, including Freeman’s replaced it with a V-shaped stone and mortar dam with one sluiceway. The stone was locally quarried. Its height is unknown but it measures 20 feet across and is wider at its base than at its top. Built to promote stability, the up-river side is angled with a base width of 12 feet and a top width of approximately 2 feet. In contrast, the downriver side of the dam is vertical, allowing for a sheet-like waterfall. The original sluiceway, an opening in the dam that allowed the miller to control water flow was operated by walking out over the dam and putting up planks that acted as a gate.
In 1947, Lewis Swann, an engineer by training, added a three foot concrete and stone cap to the 1918 stone and mortar dam. Silt had collected in the millpond, and Swann wished to build up more head or "Fall" to compensate for this. The cap contained several sluiceways with wooden gates to control the water. Swann also added a concrete wall to the raceway. He expanded the millpond, and created an overflow area or waterfall with short concrete steps that fan out and then deliver water to the mill. The stepped area was built for Mr. Swann’s enjoyment. He lived across the road, and liked to listen to the water moving over the steps.
In 2003, a flood event destroyed the concrete cap as well as portions of the stone and mortar dam below."