He left the property to his son, Frederick, who married a daughter of Augustus Jay (ancestor of Chief Justice John Jay). Frederick built in 171S the line Yan Cortlandt mansion, which, together with the then existing residue of the estate, was purchased by the City of Xew York in 1889, the land being converted into a public park (Yan Cortlandt Park) and the mansion placed in the custody of the Colonial Dames of the State of New York, and by them utilized for the purposes of a historical museum. Jacobus Yan Cortlandt, the ancestor of the Yonkers Van Cortlandts, also owned a large estate in the Town of Bedford, part of which descended to Chief Justice John Jay and is still in the possession of the Jay family. Our narrative, from the period when the active acquisition of the lands of Westchester County began, about the time of the English conquest (1661), has naturally followed the course of the progressive new purchases and occupation running from the seat of the already settled localities on the Sound westward and northward along the formerly unpurchased or undeveloped shores of the Harlem River, Spuyten Duyvil Creek, and the Hudson. Pursuing this natural course, our attention has been mainly claimed by the great land grants of Morrisania, Fordham, Philipseburgh, and Cortlandt Manors, extending consecutively from near the mouth of the Bronx to Anthony?s Nose, and covering substantially the whole of the western half and northern section of the county. The reader has, of course, borne in mind that throughout the period we have traversed in tracing the originial land acquisitions under English rule in the western division of the county -- that is, a period reaching to the end of the seventeenth century, -- the more complete settlement of the already well-occupied eastern division was steadily proceeding, and, besides resulting in the constant upbuilding of the little communities on the Sound, was incidentally bringing all previously neglected districts of the interior, up to the confines of Philipse's and Van Cortlandt's lands, under definite private ownership, and distributing through them an enterprising and energetic element of new settlers.