Old Croton Dam, Site of
Also known as: New Croton Dam; See Also:Downtown Ossining Historic District
Why it's listed
Beneath the waters of the New Croton Reservoir in Westchester County lies the Old Croton Dam, built between 1837 and 1842 under engineer John Bloomfield Jervis. A gravity dam of rubble core with granite ashlar facing, it ran 670 feet long and 57 feet high, backing the Croton River up about five miles to form a reservoir of roughly 400 acres. It fed the Old Croton Aqueduct, which brought water to New York City. Described as the first large masonry dam in the United States, it served as a model for later municipal water supply dams in the east. When the New Croton Dam was completed in 1906, the older structure was submerged, though it remains intact and was briefly exposed in 1956. The nomination also covers the New Croton Dam, a 1,168-foot masonry structure with buttresses, arches, a curved spillway and a steel arch bridge, praised for combining engineering with architectural design beside Croton Gorge park.
Significance in brief: The Old Croton Dam was the first large masonry dam in the United States and a model for municipal water supply dams in the eastern states. It was the key link to the Old Croton Aqueduct and is notable as an intact underwater archeological site. The New Croton Dam is cited as a major engineering work of notable design and as the largest pure masonry dam.
Machine-generated summary. This summary was generated by a language model from the official nomination document and has not been reviewed line by line by an editor. It may contain errors. Check the source document before relying on any detail. Source: nomination document (PDF) · National Archives catalog entry. NRHP reference 73001289, listed June 19, 1973. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | N of Ossining on NY 129, Ossining |
|---|---|
| County | Westchester County |
| Listed | June 19, 1973 |
| Reference number | 73001289 |
| Resource type | Site |
| Period of significance | 1837-42 (Old); 1893-1901-06 (New) |
| Architect / builder | John Bloomfield Jervis (Old Dam engineer in charge); New Dam engineers Alphonse Fteley, William R. Hill, J. Waldo Smith and Walter H. Sears |
| Areas of significance | Engineering, Architecture |
| Level of significance | National |
| Status (as stated in the nomination) | Old dam is submerged in the New Croton Reservoir and still intact; it was exposed briefly when the reservoir was lowered in 1956. New Croton Dam remains part of the New York City water supply, rated excellent condition. |
| Acreage | 110 |
| Coordinates | 41.22623, -73.85541 (NPS GIS) |
What listing means for this property
Sites (archaeological sites, battlefields, landscapes) are often listed with a restricted address to protect them from looting or disturbance. Listing is honorary for private owners; federal undertakings on or near the site go through Section 106 review, and state laws may protect burials and artefacts regardless of listing.
General information, not legal or tax advice. Rules change; confirm with your State Historic Preservation Office or a qualified adviser.
Sources and further reading
- National Park Service, National Register of Historic Places database (snapshot May 2026), reference 73001289.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q7531782
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.