The early success of Waterloo and Cedar Falls was due largely to their being good locations for dams and mills. The milling industry was active in both communities up until the 1920s.

Millstones were part of every flourmill. These were sets of upper and lower circular stones that did the actual grinding. Wheat, corn, oats and other grains were fed into the stones through a hole in the upper stone. The grain was ground by the rotation of the two stones against each other, with the flour emerging from between the edges of the stones.

The two millstones were originally part of the Miles Stafford Mill, built in 1857, on the site of the present Homeland Bank in Waterloo. When the mill was torn down in 1924, Henry Grout obtained the stones for his collection of historical items. The stones were placed on the walk near the river all next to the YMCA building. In 1981, through the efforts of the Cedar Valley Historical Society, they were moved to their permanent location in the park.

Note that both millstones are upper millstones, since they both have holes in their centers.