The enlargement[5] was completed in 1906 as a part of a system of reservoirs designed to attract water from Putnam and Westchester Counties (the Croton Watershed) to New York City.

[6] Kensico was surrounded by hills that came to a natural V-shape, making it an ideal area to hold a vast amount of water.

A seventeen-mile railroad spur and a small network of highways were built to carry materials from quarries at nearby Cranberry and Silver Lakes to the dam site.

On July 12, 2018, the New York City Department of Environmental Protection (DEP) press office announced plans for a Kensico-Eastview Connection Project.

[7] The project mainly involves constructing an approximately 2-mile long tunnel between the Kensico Reservoir and the nearby Catskill/Delaware Ultraviolet Light Disinfection (CDUV) Facility.

Crews were largely made up of Italian immigrants, who were tasked with digging straight down to a depth of 110 feet (34 m) to reach solid rock with no water-bearing seams.

The tremendous influx of workers and their families provided a period of growth for the surrounding area, spurring new stores, rooming houses, hotels, restaurants and saloons.

The Kensico Reservoir was acquired as parkland in 1963 from the New York City Watershed Commission and remains the property of the DEP.

After leaving Kensico, the water is treated with ultraviolet light at the New York City Department of Environmental Protection's Eastview facility, then continues on to Hillview Reservoir.

Shore fishing is practiced in many areas, and boating is restricted to Department of Environmental Conservation licensed and inspected aluminum rowboats.

Historically, Westchester County's Department of Parks has hosted several community-wide events at the plaza, including outdoor screenings throughout the summer and early autumn, and a Fourth of July celebration with fireworks, food trucks, and live music.