Ossining Weir

Structure/Property Name (Current and Original, if Different): Ossining Weir
Street Address/Location: Intersection of Ann Street and the trail of the Old Croton Aqueduct State Historic Park
Town/City: Ossining
County: Westchester
Owner: Presumably owned by the New York State Office of Parks, Recreation & Historic Preservation, since it is built along the Old Croton Aqueduct State Historic Park

Architect/Engineer/Other Responsible Parties: B. S. Church, engineer
Historic Use: According to the Merriam-Webster dictionary, a weir is a “a dam in a stream or river to raise the water level or divert its flow.” The weirs along the Old Croton Aqueduct were small structures that were built right over or next to the aqueduct, allowing the weir tender to have direct access to the aqueduct tunnel. The weirs had secondary tunnels that could direct water from the main aqueduct channel into nearby streams if the water flow was too high. The weir tenders could control the aqueduct’s water in three ways: 1. Altering the heights of boards to control the aqueduct’s water depth; 2. Dropping stop planks in the aqueduct to completely block its flow; and 3. Opening screw gates to get rid of water in one section of the aqueduct.
Present Use:  The weir is open for tours throughout the year to give the public increased awareness and education about the Old Croton Aqueduct. The New Ossining Weir may be the place where the public can actually see and enter the aqueduct itself as well.
Typology: Weir
Architectural Style: Egyptian Revival
Period(s) of Construction: 1881–86
Date of Decommissioning: 1965 (closing of the Old Croton Aqueduct as a functioning water system)
Date(s) of Demolition: n/a
Structural System/Materials: Granite, bronze, cast iron
Significant Alterations: Signage and walkways were added to the weir to allow visitors to tour the weir and the aqueduct, probably sometime during the 1980s or 1990s

Brief Architectural Description: Like several other structures that are part of the Old Croton Aqueduct, the weirs are built in an Egyptian Revival style, chosen for its associations with permanence and because its forms could be easily created by stonemasons. All of the weirs have pilasters along their corners, belt coursing, and a projecting cornice. The weir has a single metal-door entrance, no windows, and a ventilating hole in its brick-arched roof. The New Ossining Weir is twenty feet long, ten feet wide, and thirty feet high, including the portion of the weir that is built underground for the waste-water conduit.

Brief Statement of Historic Significance: Weirs have been in use since the early twelfth century to control waterways, and the Old Croton Aqueduct’s waste weirs are a continuation of the long history of this typology. The aqueduct’s weirs serve as some of the larger visible elements of the system along its path. While six weirs had been built along the Old Croton Aqueduct when it was first constructed in the late 1830s and early 1840s, it was decided to increase the functionality of four of these weirs in the 1880s, making it possible not only to divert water and control its depth, but to stop it completely at the site of the weirs. This would allow the aqueduct to be shut off in sections, making its maintenance much easier and faster. It seems that the Ossining New Weir was the only one of these later weirs that was an entirely new construction, rather than being a mere alteration to a preexisting weir, as happened in Tarrytown, Yonkers, and Kingsbridge. A new building was required in Ossining because a waste-weir pipe nearly two thousand feet long would have needed to be built if they altered the already-existing weir in Ossining.

Accessibility to Public: The weir is located along the Old Croton Aqueduct State Historic Park, so its exterior is publicly accessible. The interior is opened only for guided tours.
Landmark Status: In 1992 the Old Croton Aqueduct was awarded National Historic Landmark Status.

Threats: Vandalism
Current Interpretation: The Ossining Weir is periodically opened for tours, which are operated by the Friends of the Old Croton Aqueduct. The weir has explanatory signage in its interior that people can read during the tour, although this signage has some incorrect information and typos and doesn’t have a consistent appearance.


Historic Image



Mark R. Edwards, “The Architecture of the Old Croton Aqueduct,” Columbia HP Thesis, 1976.

John B. Jervis, Description of the Croton Aqueduct (New York: Slamm and Guion, 1842).

Robie S. Lange, “Croton Aqueduct,” National Register of Historic Places Registration Form (Washington DC: National Park Service, October 1991).

Larry D. Lankton, “Manhattan Life Line: Engineering the Old Croton Aqueduct, 1833–1842,” Historic American Engineering Record (HAER No. NY-120) (Washington DC: Prints and Photographs Division, Library of Congress, 1979).

T. Schramke, A Description of the New York Croton Aqueduct (New York and Berlin: Mundt Berlin, 1846).

Edward Wegmann, The Water-Supply of the City of New York: 1658–1895 (New York: John Wiley and Sons; London: Chapman and Hall Ltd., 1896).
Becca Salgado


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