The Pennsylvania Supply Company was founded in 1921 by Walter Mumma to provide quality building materials to contractors in Dauphin and Cumberland counties. Over the years the company expanded by acquiring quarries in new territories and producing aggregate.

In 1993, Pennsy became a member of Oldcastle Materials, Inc.. and eventually formed the Mid-Atlantic Group of companies along with, Slusser Brothers, Tilcon Delaware and Pioneer Concrete. Oldcastle is the leading vertical integrated supplier of aggregates, asphalt, ready-mix concrete and paving services in the United States and is one of four divisions of CRH plc, the international building materials group.