The Crocker-McMillin Mansion is a historic house in Mahwah, New Jersey. It was built between 1903 and 1907 on the Darling estate for businessman George Crocker. After Crocker died in 1909, the banker Emerson McMillin lived in the 75-room, three-story residence until his death in 1922. From 1927 to 1984, the mansion was occupied by the Crocker-McMillin Mansion-Immaculate Conception Seminary. The property, located at 675 Ramapo Valley Road in Mahwah, is one of New Jersey's historical landmarks. It was listed on the National Register of Historic Places in 1997.