Crocker-McMillin Mansion, Gothic Revival mansion in Mahwah, US.

The Crocker-McMillin Mansion is a 75-room, three-story house in Mahwah, built for George Crocker between 1903 and 1907 to a design by architect James Brite modelled on Bramshill House in England. Its grey stone and red brick front has a projecting entrance bay with a pointed gable and carved stone crest above a round-arched doorway, a brick wing with a stepped gable, and tall brick chimneys.

George Crocker bought the Darling estate in November 1901 and had architect James Brite design a 45,000-square-foot mansion modeled on Bramshill House in England; it was completed in 1907. After Crocker died in 1909, banker Emerson McMillin lived there until 1922. The Immaculate Conception Seminary occupied the building from 1927 to 1984.

The mansion served as the Immaculate Conception Seminary from 1927 to 1984, transforming it into a center for religious education and training. The grand rooms were repurposed for study and prayer, giving the building a second life with spiritual purpose.

The estate now covers 12.5 acres (about 5 hectares), down from the original 1,100-plus acres; greenhouses, barns, stables and a gatehouse once stood on the grounds. The mansion sits at 675 Ramapo Valley Road, and the house was seized by authorities in March 2023, so access is not guaranteed.

The mansion was known for its productive vegetable gardens, whose harvest was sold in New York City markets, showing the family's connection to commerce networks. This agricultural operation was unusual for a residence of such size and prestige.