In 1840, John Jacob Astor purchased the main part (540 acres) for $42,000 and gave it to his daughter, Dorothea Langdon, her husband Walter and her 5 children. The division of the Hosack estate required adjustments to the northern part of the drive. Unfortunately, a fire destroyed the original Bard mansion in 1845. They then hired an architect referred to only as Platt of New York City to design a new mansion, which was built on the site of the original building.  

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The Langdons were not full-time residents of the Hyde Park estate. By this time, it was fashionable for the wealthy to spend different 'seasons' in New York City, Newport and Europe.After his father's death in 1847, Walter Langdon, Jr. began buying out his numerous brothers’ and sisters’ interests in the estate, as well as pieces which had been retained by Hosack’s heirs. This process was completed in 1852. 

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For the most part, the Langdon ownership was a period of benign neglect for the estate. The only major change, and it was a very major change, was moving the formal garden and greenhouse site further from the house in 1875.  

The new site was a hillside overlooking the Crum Elbow Creek. Greenhouses and a potting shed were built on the west side of the garden, near the crest of the hill, while a toolhouse and cottage for the head gardener were built on the north side. Because of the sloped site, terraces were constructed for the proper layout of formal garden beds. In total, there were two greenhouse terraces, and four garden terraces. The entire site was enclosed by brick walls. With the exception of the greenhouses, these structures still exist today.

 

After Walter Langdon’s death in 1894, his heirs sold the property to Frederick and Louise Vanderbilt.

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