The area studied in the 2002 update encompasses the Highlands physiographic province in New York and New Jersey, the extent of which is bounded by the New Jersey/Pennsylvania border (southwest) and the New York/Connecticut border (northeast). This represents an expansion of the 1992 boundary from the eastern shore of the Hudson River to the western Connecticut state line, including all of Putnam County and portions of Dutchess and Westchester Counties in New York.
The Highlands physiographic province was outlined by the USDA Forest Service using topography and geology as key determinants. The final study area was then expanded to include the entirety of municipalities that fell only partially within the province boundary, as well as those that were wholly subsumed by it. Eighty-three municipalities in 7 New Jersey counties and 25 municipalities in 5 New York counties were, therefore, included in the assessment update. Neighboring areas in Pennsylvania and Connecticut may be included in future investigations.