The Water Supply Commission (1833-1849) was formed to supply the city of New York with pure and wholesome water. Extensive investigations to locate a clean, reliable water source that could be conveyed to the city by gravity led them to the Croton River in Westchester County. Under the direction of Chief Engineer John Jervis, the Croton Aqueduct and its supporting structures were completed enough to start delivering water in 1842, just five years after the start of construction. Raising and lowering the sluice gates shown in this drawing controlled the flow of water into the York Hill Receiving Reservoir.

It was up to the Croton Aqueduct Board (1842-1849) to maintain and operate the city’s new water utility, including nearly 200 miles of pipes that delivered water under city streets to consumers. The Board also completed construction projects including the extraordinary High Bridge which carried the Croton Aqueduct across the Harlem River. Disputes over the height of the bridge forced the State Legislature to intervene and delayed its completion until 1848. This drawing shows the cofferdams and scaffolding required to build the vertical piers and arches.

With the Croton System completed, the Croton Aqueduct Department (1849-1870) was created to protect its structures and ensure that clean water continued to flow into the city without interruption. It also took on sewer construction. Water consumption outpaced supply so quickly that the Department started building another in-city reservoir in 1858, integrating it into the design for Central Park with a more naturalistic contour replacing the original rectangular plan.

The Department of Public Works (1870-1898) operated the Croton water supply and built the new Bronx and Byram Rivers system, including Williamsbridge Reservoir. Reservoir “keepers” lived in houses onsite, serving as guards and overseeing operations. The Williamsbridge Reservoir Keeper's House is the only surviving building in New York City associated with the Bronx and Byram system. Architect Douglas Smyth’s design was not built; Public Works opted for a simpler structure.

As the city continued growing, the Aqueduct Commission (1883-1910) was organized to increase the city’s water supply by building new dams and reservoirs in the Croton River watershed, and a new aqueduct to transport the water to the city. Construction of the New Croton Aqueduct began in 1885, and by 1890, water flowed through the 135th Street Gate House toward Central Park's receiving reservoirs and into the city's distribution system.

The Department of Water Supply (1898-1901) replaced Public Works when the city was unified in 1898, taking over its duties along with responsibility over the waterworks of the former City of Brooklyn and the public water supplies serving Queens and Staten Island. Its most pressing job was to consolidate and enlarge the new five borough city’s water distribution system, a massive administrative and logistical task. It had repair company garages throughout the city, like this one serving the 2nd Ward in Queens.

The Department of Water Supply, Gas and Electricity (1902-1968) grew out of the Department of Water Supply, taking on additional duties implicit in its name. During its tenure, the City assembled the Burr-Hering-Freeman Commission to evaluate existing water supplies and future needs. Its nearly 1000-page report became the roadmap for the Catskill and Delaware water systems that were to come. Additional water was at least a decade away, though, so fire protection became a priority for the city. Between 1904 and 1908, the Department built the first phase of the High Pressure Fire Service system. Its pumping stations, water distribution pipes, and fire hydrants were dedicated exclusively to protecting the city’s manufacturing, storehouse, and office buildings in Manhattan and Brooklyn, and the resort area of Coney Island.

With the Burr-Hering-Freeman Commission investigation completed, the Board of Water Supply (1905-1978) was formed to plan and build another system of reservoirs and tunnels that would ensure access to clean water for the growing population. Most of the DEP archives came from the Board of Water Supply, whose meticulous recordkeeping practices, supported by full-time librarians and catalogers, ensured the records would retain long-term value. The Board recognized the importance of thoroughly documenting its monumental engineering projects, creating thousands of photographs and drawings.

Each Borough President’s office held responsibility for sewage treatment before this essential task was transferred to the Department of Sanitation. Its Bureau of Sewage Disposal and Intercepting Sewers (1929-1937) built the City’s first two modern sewage treatment facilities, at Coney Island in 1935 and Wards Island in 1937. The Wards Island Intercepting Sewers in the Bronx, shown here under construction, received wastewater from sewer lines and conducted it toward the treatment plant. Borough Presidents continued building and maintaining sewer lines.

Responsibility for the design, construction, and operation of sewage treatment facilities and intercepting sewers was transferred from Sanitation to a new Department of Public Works (1938-1968). The DPW built several more treatment plants and operated the first three motorized sludge vessels, which transported sludge—the organic material removed from wastewater—out into the ocean to keep the local waters clean. (Ocean dumping ended around 1990 and since then sludge has been transported by vessels to plants with the infrastructure needed to finish the treatment process.)

The New York City Environmental Protection Administration (1968-1977) combined all of the city departments concerned with air, water, solid waste, and noise pollution into a single “super-agency.” It was one of the first, if not the first, environmental agencies in the country. In 1977, solid waste management was transferred to a new Department of Sanitation and the Department of Environmental Protection assumed control over everything else. City Water Tunnel No. 3 is the largest capital construction project in New York City history. Construction started in 1970 and is still underway, with parts of the tunnel put in service decades ago.