The Contra Costa County Historical Society is a membership-based, non-profit organization with a mission to preserve, protect, and provide public access to the records and heritage of Contra Costa County, California. The Contra Costa County Historical Society operates the County History Center, located at 724 Escobar Street in downtown Martinez. The History Center collection consists of records and artifacts concerning the history of Contra Costa County, California. A large part of the collection includes early county court and probate records, naturalization records, supervisor records, tax assessor records; maps, photographs, newspapers and newspaper clippings, and special collections of some prominent local government officials and historians. Operating hours of the History Center: Tuesday 9:00am - 4:00pm Wednesday 9:00am - 4:00pm Thursday 9:00am - 4:00pm 1st and 3rd Saturday 10:00am - 2:00pm To schedule an appointment for a tour or to meet with a researcher, call (925) 229-1042.