In 1917, five companies joined to form Union Carbide, which later became a leader in making chemicals from natural gas and oil. It first set up operations at Clendenin in northern Kanawha County. In the 1920s, it relocated to South Charleston, built a large plant, and began producing important chemicals like ethylene and propylene. By the 1960s, Union Carbide made hundreds of chemicals and plastics, including ingredients for popular products like antifreeze and batteries.

The company grew to be one of the biggest in the U.S., employing about 12,000 people in West Virginia. But in 1984, a disaster at a Union Carbide plant in India killed thousands and hurt many more, causing worldwide safety concerns. After this, Union Carbide sold many parts of its business. In 2001, Dow Chemical bought Union Carbide, ending its history as its own company.