Slate Industry. One of the largest slate-producing centers in the United States. Welsh slate entrepreneur William Roberts first sighted slate in 1844 near a local barn. He and other Welsh immigrants established and worked in numerous slate quarries in this region. Nearby quarries included "Big Franklin"( c.1852), the largest excavation in Slatington; and "Williams," known for its production of school slate. These sites also contributed to the increase of slate roofing during the late 19th century.