Donated to the city in 1913 by C.C. Pennock of the Committee for Pioneer Association.
The inscription on the front of the monument reads: "First Quartz Mill used in Boulder County, July 1859, by W. R. Balre, M. L. McCaslin. D. Horsfal, Pioneer."
Mr. Pennock said "$50,000 in free gold was taken out of this hollow in the rock, by grinding the quartz and washing." It is believed the mill was located near Gold Hill in the area above Boulder.