The Catskills were more desirable, as state-owned Forest Preserve land in the region could not, under the state constitution, be sold to any other party.

A recent amendment to that section of the state constitution also allowed up to 3 percent of the total Forest Preserve land to be flooded for reservoirs.

The Ashokan Reservoir was constructed between 1907 and 1915, by the New York City Board of Water Supply, by impounding the Esopus Creek.

The area that became the West Basin of the reservoir contained 504 dwellings, nine blacksmith shops, 35 stores, 10 churches, 10 schools, seven sawmills and a gristmill.

The dam was constructed mainly by local laborers,[citation needed] as well as African-Americans and Italian immigrants, who also did the job of razing most of the trees and buildings in the area.

When the dam was completed, giant steam whistles blew for one hour, signaling to people in the valley to evacuate immediately.

The resulting body of water is the oldest New York City–owned reservoir in the Catskill Mountains, being placed into service as long ago as 1915.

Due to the need to ensure the safety of the water system, and to make sure the nearly century-old dams stay intact, only limited activities are permitted around the reservoir property, including fishing and logging.

After the September 11 attacks, the city and state decided to permanently close the spillway road to vehicular traffic as a security precaution.

This has added a great deal more traveling time and distance for those on the south side of the reservoir to reach locations to the north.