Merck is a multinational pharmaceutical company. The name Merck is in fact used by two separate pharmaceutical companies, one in the United States (Merck & Co, Inc) and in Europe (Merck KGaA). During World War I, the German company's American operations were seized and ties between the two companies were severed.
Merck & Co has sales of making it alone one of the largest pharmaceutical companies in the world. It is headquartered in New Jersey.
A key Merck product, the painkiller Vioxx used to treat arthritis and other conditions causing chronic pain was withdrawn after it shown to increase the risk of heart attack and death in long term use.