Alvan Clark & Sons was an American maker of optics that became famous for crafting lenses for some of the largest refracting telescopes of the 19th and early 20th centuries. Founded in 1846 in Cambridgeport, Massachusetts, by Alvan Clark (1804–1887, a descendant of Cape Cod whalers who started as a portrait painter, and his sons George Bassett Clark and Alvan Graham Clark. Five times, the firm built the largest refracting telescopes in the world. The Clark firm gained "worldwide fame and distribution", wrote one author on astronomy in 1899.