Mining at the Highland Mills quarry began circa 1945, with sand and gravel mining performed by the Cooney family, who were prominent regional aggregate suppliers. After a series of intervening transactions, the operation was purchased by Speyside Holdings LLC, a private equity consortium that is presently mining its consolidated deposits to produce a full suite of coarse and fine aggregates. As the result of a rigorous capital plan implemented by Speyside Sand & Stone's management, Speyside Sand & Stone is now a full service fine and coarse aggregate producer that serves the New York City, Hudson Valley, and Long Island concrete, asphalt, and site work industries.