POSCO (formerly Pohang Iron and Steel Company) is a South Korean steel-making company headquartered in Pohang, South Korea. It had an output of 42 million tonnes of crude steel in 2015, making it the world's fourth-largest steelmaker by this measure. In 2010, it was the world's largest steel manufacturing company by market value. Also, in 2012, it was named as the 146th world's largest corporations by the Fortune global 500. POSCO currently operates two integrated steel mills in South Korea, in Pohang and Gwangyang. In addition, POSCO operates a joint venture with U.S. Steel, USS-POSCO, which is located in Pittsburg, California, United States.