The winery is located in Healdsburg in the Californian Alexander Valley (Sonoma County region). The historic estate was founded in 1876 by two Tuscan wine brokers, Giuseppe and Pietro Simi. From 1904 the winery was run by Giuseppe's daughter Isabelle. With foresight, Isabelle continued the production during the American prohibition from 1920 to 1933 and stored the wines in the cellar. Therefore, Simi was one of the few companies able to sell wine at the end of the prohibition. Isabel Simi sold the business in 1970 to the oil magnate Russel Green, who sold it to Michael Dixon in 1973. Simi's heyday began in 1979, when Dixon hired Mondavi's oenologist Zelma Long. She carried out a series of quality-enhancing measures. These included stainless steel tanks instead of the large wooden vats and French barriques for ageing the wines.