Merck & Co. , Inc. , d.b.a. Merck Sharp & Dohme, MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. Merck headquarters is currently located in Whitehouse Station, New Jersey and will be relocating to Summit, New Jersey shortly. The company was established in 1891 as the United States subsidiary of the German company now known as Merck KGaA. Merck & Co.