The Catskill Mountains, also known as the Catskills, are a physiographic province and subrange of the larger Appalachian Mountains, located in southeastern New York. As a cultural and geographic region, the Catskills are generally defined as those areas close to or within the borders of the Catskill Park, a 700,000-acre forest preserve protected from many for…The Catskill Mountains, also known as the Catskills, are a physiographic province and subrange of the larger Appalachian Mountains, located in southeastern New York. As a cultural and geographic region, the Catskills are generally defined as those areas close to or within the borders of the Catskill Park, a 700,000-acre forest preserve protected from many forms of development under New York state law.