Dow Chemical (NYSE: DOW) is a diversified chemical company. It is headquartered in Midland, Mich. and was founded in 1897.
Book: “Growth Company: Dow Chemical’s First Century,” by E. N. Brandt, Michigan State University Press, East Lansing, MI, 1997. See the review posted on Motley Fool's Books--Non-fiction discussion board: 
Dow is a large diversified, global chemical company with numerous plants and product lines. Its major business units are--
Consumer and Lifestyle
Infrastructure and Transportation
The company was founded by Herbert Dow to extract bromine from the salt domes of Michigan. That required chlorine to convert natural bromide to volatile bromine. The company was an early user of electrochemical cells to make chlorine from salt. It also sold chlorinated lime (now called calcium hypochlorite) an early disinfectant and the original agent used to chlorinate drinking water. Later chlorinated solvents were developed including chloroform, trichloroethylene, the vapor degreaser for metals, and Permachlor, the non flammable dry cleaning solvent. The company is famous for an integrated system that allows it to recover and recycle byproduct chlorides on its major sites.
Later its business evolved to include plastics like polystyrene.
In recent times the company has focused on selling off it low margin commodity businesses and adding specialty chemicals lines through acquisitions. Its major acquisitions include Union Carbide and Rohm & Haas (2009). In 2010, Dow sold its styrenics business to Bain Capital. The styrenics business presumably included styrene monomer, polystyrene, and styrene co-polymers such as ABS. In 2011, the polypropylene business was sold to Braskem.
As Dow sheds its commodity businesses, agricultural products become more important. For those who supply seeds in the ag sector, corn is king. Wall Street Journal on Feb 26, 2014, gave 2013 market share as Dupont, 35%; Monsanto, 35; AgReliant, 6; Syngenta, 6; Dow, 4; others 14%.