Winchester is a census-designated place (CDP) in Riverside County, California, USA. As of the 2000 census, the CDP had a total population of 2,155. 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. However, construction and growth slowed when the housing bubble burst in 2007, resulting in a housing market correction. In October 2008, the town was rocked by the brutal murders of Marine Corps Sgt. Jan Pawel Pietrzak and his wife, Quiana.