Merck & Co., Inc. (NYSE: MRK), d.b.a. Merck Sharp & Dohme (MSD) outside the United States and Canada, is an American pharmaceutical company and one of the largest pharmaceutical companies in the world. Merck headquarters is located in Kenilworth, New Jersey. The company was established in 1891 as the United States subsidiary of the German company Merck (founded 1668). Merck & Co.