The History of the Several Towns, Manors, and Patents of the County of Westchester (1881 revised edition, Vol. I)
John Peter De Lancey by will (dated 28th of January, 1823) devised his property in this town to Thomas James De Lancey, the only child of his deceased son Thomas James, and to his son William Heathcote De Lancey the Bishop of Western New York (except a portion of the western end of De Lancey's Neck which he had conveyed in his life time to his deceased son Thomas James, who had devised the same to his only child Thomas James the younger). All the property of Thomas
THE TOWN OK MAMARONECK.
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James the younger lay upon the western part of de Lancey's Neck. The eastern part of that Neck, the Heathcote Hill tract, and sedge lots, with the other lands of John Peter de Lancey in Mamaioneek passed to the late Bishop de Lancey," who devised the same to his four surviving children, Edward Floyd, John Peter, William Heathcote, Jr., and Margaret, wife of Thomas F. Rochester, M. D. The Heathcote Hill estate was devised to them equally, and subsequently by purchase of the shares of his brothers and sister became the sole property of Edward Floyd de Lancey, the present proprietor. Thomas James de Lancey, the younger sold his part 01 de Lancey's Neck in his lifetime, and it is now held by many owners -- among whom are James M. Constable, John Greacen, Leonard Jacob, Mrs. Eldridge and others. The eastern part, except a small portion in the rear sold to Mrs. E. V. Rushmore, is still held by the children of Bishop de Lancey, the extreme south-eastern part being the country seat of Edward F. de Lancey.