Originally named the Chappaqua Historical Society, the Society was founded in April 1966 on the 175th anniversary of the formation of the Town of New Castle.

In 1968, The Chappaqua Historical Society found its home in three tiny rooms upstairs at the Holmes & Kennedy building, across from the Horace Greeley House. Rented for $25 per month, the ceiling in one room was so low that it was difficult to stand up. The NYS Department of Education granted the Society’s permanent charter in 1969.

In early 1971, the Society relocated to a 300-square-foot space in the new Town Hall. During this time, the Greeley Family Collection (furniture, books, paintings, etc.), purchased by the community from Greeley Stahl, Horace Greeley’s great-grandson, was officially turned over to the Chappaqua Historical Society for its museum. The Society set up exhibits at the Chappaqua Library and held its first public meeting at the First Congregational Church.

The Chappaqua Historical Society officially changed its name in 1984 to the New Castle Historical Society to express more effectively its role as a historical society for the entire town.

Between 1985 and 1990, due to a lack of space in the Town Hall, the museum was moved to a variety of local schools, first Roaring Brook Elementary School, then Robert E. Bell Middle School and finally Horace Greeley High School.

On February 25, 1991, the New Castle Historical Society took ownership of 312 King Street, creating its first headquarters and museum. The building was dedicated in 1992 and the Society remained in that location until 1998.