A Merck grandson handed the family's American shares to the US government in 1917, and the two Merck companies have fought over the name ever since

In 1668 Friedrich Jacob Merck bought the Engel pharmacy in Darmstadt. The business grew into the family partnership E. Merck. In 1887 it opened a sales office in New York. In 1891 George Merck, 24, a grandson of Heinrich Emanuel Merck, joined the American branch. It built a plant at Rahway, New Jersey, from 1899. After the United States entered the First World War, George Merck, fearing anti-German feeling, handed E. Merck's block of shares to the Alien Property Custodian. After the war the custodian sold the shares, worth about $3 million, to the public. That ended the German family's ownership. A 1932 agreement split the name: Merck & Co. took the United States and Canada, E. Merck the rest of the world. The US government sued, and a 1945 consent decree in New Jersey cancelled the agreement. New agreements followed in 1955 and 1970. In 2016 the English High Court found that the American company's use of "Merck" in the UK breached the 1970 agreement. On 28 March 2025 the Court of Appeal upheld further findings of breach. The Merck family still holds about 70% of Merck KGaA in Darmstadt. George Merck died in 1926; his son George W. Merck had become president in 1925.