There is no town in Westchester County of New York State named Philipsburg. "Philipsburg NY" refers to the Manor or estate purchased in about 1693 by Frederick Philipse with permission of the King of England. The estate was 52,000 acres along the east bank of the Hudson River. Frederic built a manor house at the confluence of the Pocantico and Hudson Rivers.
The manor lands were leased to farmers. While all the lands were owned by the Lord of the Manor, the buildings erected by the farmers belonged to them and were regularly sold or bequeathed to others.
As you can see from the map below, in the immediate neighbourhood of the Manor are Tarrytown and Sleepy Hollow.
Below is a modern photo of the Manor house and the mill.