The complex New York City water supply system—with 19 reservoirs bringing mountain water from as far as away through a gravity-fed web of aqueducts — consists of three different systems. The Croton system, the oldest and smallest section, sits in Westchester and Putnam Counties. The second oldest is the Catskill system. In the early years of the 20th century, the city and state designated thousands of acres the eastern Catskills to build two reservoirs that more than doubled the city's capacity. In the 1950s and 1960s, the city expanded again, tapping the east and west branches of the Delaware River and other tributaries to create the newest and largest of its three systems.