Side A: Attracted by the availability of raw materials and railroad transportation, the Pittsburgh Plate Glass Company (PPG) built a plant here in 1899 to make soda ash for the company’s glassmaking operations. This plant began production in 1900 as the Columbia Chemical Company and represents the beginning of PPG’s diversified chemical manufacturing operations. During the 20th century this plant operated the world’s deepest (at 2,200 feet) limestone mine and manufactured commodity chemicals such as chlorine, caustic soda, and calcium chloride. By 2000, manufacture of specialty chemicals for the optical, pharmaceutical, printing, and rubber industries superseded mining and commodity chemical manufacturing. PPG’s reclamation of its former soda ash waste disposal sites, known as “lime lakes,” has won recognition for environmental stewardship.