The Silica deposits of Ottawa,Illinois is a mineral found in a geologic formation known as St Peter sandstone. This deposit is found in Ottawa and 10 miles west. It is also present in the Fox River Valley. The characteristics of Saint Peter sandstone include: deposits are soft and easy to mine; the sand is high quality silica; because of its purity, it can be cheaply mined; it is located near the surface. Major sand mining occurred in the 1890’s. It appears the majority of the sand mined was transported by rail. Several mining operations occurred in the area. The largest of the s was Ottawa Silica Company. This continues in operation today as United States Borax and Chemical Company of Los Angeles and later the U.S. Silica Company.