The Old Croton Dam is a historic dam located in Yorktown, Westchester County, New York, now lying submerged beneath the waters of the New Croton Reservoir. The dam was built on the Croton River between 1837 and 1842, and was the first substantial masonry dam in the United States. Construction was delayed by a January 1841 storm that washed awa…The Old Croton Dam is a historic dam located in Yorktown, Westchester County, New York, now lying submerged beneath the waters of the New Croton Reservoir. The dam was built on the Croton River between 1837 and 1842, and was the first substantial masonry dam in the United States. Construction was delayed by a January 1841 storm that washed away most of the dam, with heavy downstream damage and loss of life.