Within the bounds of the town of Hillsdale are the headwaters of several small streams, the Copake Creek, the Claverack Creek, the Roeliff Jansen Kill, and tributaries of Green River, which flows across the northeastern boundaries of the town.
There were three fulling mills on the Roeliff Jansen’s Kill, and two carding machines in the vicinity, all in what was then called the Collin neighborhood. The disastrous flood of 1888 destroyed what was remaining of them at that time.
Both the Roeliff Jansen Kill and Roeliff Jansen Park outside Hillsdale were named after Roeliff Jansen - the Roeliff Jansen Park entrance is located on Route 22, one half mile south of the Hillsdale light on the east side of the road. The park includes multiple trails, access to the Roeliff Jansen Kill, several picnic areas, a dog run, a farmers market, a summer youth program, and much more.