During the 1850s and 1860s, rock was quarried from the area encompassed in Rockville Hills Regional Park. The stone at Rockville was volcanic tuff, a light gray rock that was soft enough to cut easily but hardened once it was excavated. Called "absolutely fireproof," the rock was used in a number of local structures.
In the rock on the other side of Rockville Road, you can see tooling marks.