From 1940 to 1941, Dow built its first plant in Freeport, Texas to produce magnesium extracted from seawater rather than underground brine. The Freeport plant is Dow's largest site – and the largest integrated chemical manufacturing site in the country. The site grew quickly – with power, chlorine, caustic soda and ethylene also soon in production. Growth of this business made Dow a strategic business during World War II, as magnesium became important to manufacture lightweight parts for aircraft. Based on 2002–2003 data, the Freeport plants produced 27 billion lbs of product – or 21% of Dow's global production. In 1942, Dow began its foreign expansion with the formation of Dow Chemical of Canada in Sarnia, Ontario to produce styrene for use in styrene-butadiene synthetic rubber. Also during the war, Dow and Corning began their joint venture, Dow Corning, to produce silicones for military and, later, civilian use.