In the early 1900s, new technology changed how window glass had been made for centuries. Skilled workers—many from France and Belgium—started small, family-owned glass plants in Clarksburg and South Charleston. French and Flemish were spoken in neighborhoods near these factories. But by the 1920s, new machines were taking over all parts of the glassmaking process except the final stage: cutting it. Big companies began mass-producing window glass. Some of these, most notably Pittsburgh Plate Glass and Libbey-Owens-Ford, opened plants in West Virginia that kept the industry going through the 1970s.

Between 1947 and 1963, West Virginia was responsible for 15% to 21% of the flat glass produced in the United States.