Old Croton Aqueduct, Ventilator Number 9, Spring & Everett Streets, Ossining, Westchester County, NY

Significance: The Old Croton Aqueduct is an outstanding example of 19th century civil engineering and was New York City's first municipal water project. Ventilators played an important role in the function of the Old Croton Aqueduct. Allowing air into the system prevented a build up of pressure, or a vacuum and maintained the freshness of the water.
Unprocessed Field note material exists for this structure: FN-20
Survey number: HAER NY-111
Building/structure dates: 1840 Initial Construction
National Register of Historic Places NRIS Number: 74001324