Winchester is a census-designated place in Riverside County, California, USA. Winchester was founded in 1886 in Peasant Valley in what was then San Diego County. The town was named after the widow of Horace Winchester, Mrs. Amy Winchester. Largely rural for most of its history, and home to agricultural businesses including the Winchester Cheese Company, Winchester experienced rapid growth during the housing construction boom in the early-to-mid 2000s. As of the 2010 census, the population of 2,534, up from 2,155 at the 2000 census.