New York City's Board of Water Supply began planning for the Catskill water supply system early in the 20th century, and celebrated completion of the first phase of construction in 1917. This ambitious project involved the waters of the Esopus Creek, one of the four watersheds in the Catskills, and expanded to the Ashokan Reservoir and the Catskill Aqueduct. The city's Department of Water Supply, Gas, and Electricity assumed responsibility for its operation and maintenance upon completion. A later expansion of the system concluded in1928, involved the construction of the Schoharie Reservoir and the Shandaken Tunnel. The photographs presented here range in date from about 1906 to 1915.