WCHS was founded in 1874 as a member-based, not-for-profit agency incorporated by the State of New York to serve the people of Westchester. The mission of WCHS is to collect and preserve books and pamphlets, maps, manuscripts, photographs, newspapers, and periodicals pertaining to the history of Westchester County, to promote the knowledge and understanding of that history, and to advocate for the preservation of the county's architectural heritage.