“Hillandale” on the Mendham Township/Gladstone border was built in 1906 by architect Grosvenor Atterbury for George Rudolf Mosle (1865-1941), who made his fortune in the sugar industry. In 1926, the mansion was sold to the Sisters of St. John the Baptist, the same order who later owned Blairsden in Peapack. The sisters operated an orphanage and later Mount Saint John’s Academy at Hillandale until 1992. The school buildings were then rented to the Montgomery Academy.
The convent closed in 2008 and the cemetery containing sisters’ graves was moved to Gate of Heaven Cemetery in Hawthorne, NY. Two thirds of the estate was sold to a public land trust and has been preserved as open space in Mendham Township. The mansion was demolished in 2023 to make way for a new housing development called Enclave at Hillandale.
See video from the last year of the mansion: https://www.youtube.com/watch?v=c1rZREO8JHw



I hope the open space will still be preserved. Did the trust own the mansion when it was demolished?
The trust bought the open land (athletic fields and woodland). The site of the buildings was sold to a developer.
Does anyone have information about who the builder was? All the records from my Dad’s business were tossed when he closed it, but I wonder if my grandfather, Joseph Dobbs, might have built this home. He built many large estate houses in the area, but I can only identify a handful of them. I never got to ride around with my Dad, Harold Dobbs, and record his memories of them, he knew them all. 🙁
Hi Doug, I asked around and couldn’t find any info on the contractor for Hillandale. One of our members guessed that Mosle and Atterbury may have used the Sturgis Bros. of Morristown or even a Newark or NYC contractor. Morristown Library may have more information on Sturgis Bros., but that might not get you any further in connecting Hillandale with Dobbs. I’ll let you know if we find anything further.
I appreciate the efforts you’ve made. Thank you so much! I’ll take some time when I get up to visit and see what I can find there. Much obliged!
Does anyone know the location of the Mosle Estate’s carriage house?
When the Sisters opened the orphanage it was used as a boy’s dormitory until it was destroyed by a terrible fire in November 1927.
I’ve been trying to find out where it was situated on the property.
Thanks
i was not a resident of the school but each august in the early to mid 1970s my high school had a 3 week football camp there. one of the best times of my youth. does anyone have any pictures of the cafateria ,football field, the canteen, the pool, or barracks that were on the property ?