On official New York State maps, a line of blue ink traces the park's boundaries through portions of four counties - Delaware, Greene, Sullivan, and Ulster. Everything inside that Blue Line is Catskill Park, but the designation is deceptive. Unlike a national park where the government owns all the land, only 41 percent of the Catskill Park belongs to the state. Another 54 percent is privately owned, and 5 percent belongs to New York City, which guards the watersheds feeding its reservoirs. About 50,000 people live permanently within the Blue Line. The boundary itself, drawn in 1904, followed not municipal borders but the survey lots of the old Hardenbergh Patent, watercourses, and railroad rights-of-way - creating a park shaped more by colonial land grants and industrial corridors than by ecology.

New York City's thirst reshaped the Catskills more profoundly than any logger or tanner. After the 1898 consolidation of Greater New York, the booming city needed water, and speculators had already snatched up rights closer to home. Officials looked north to the Catskill streams. The Ashokan Reservoir, begun in 1906 on the Esopus Creek, required the removal of entire hamlets - some, like Shokan and Olive Bridge, survive on its banks as remnants. The Esopus was dammed in 1913 and began sending water to the city two years later. Land claims dragged through area courts until 1940. Three more reservoirs followed within or near the park: Neversink, Rondout, and Pepacton. Today, every glass of water poured in Manhattan has likely passed through these Catskill mountains.

The Catskills have reinvented themselves repeatedly. The grand hotel era, epitomized by the Catskill Mountain House at North-South Lake, gave way to the Borscht Belt resorts that served Jewish families barred from gentile hotels. By the early 1970s that era was ending too, as civil rights laws opened other destinations and a younger generation felt less need for separateness. Then came Woodstock, backpackers, and a counterculture that discovered trails previously ignored for decades. Trails built by the state in the 1930s with Civilian Conservation Corps labor had fallen into such disuse that hiking writer Raymond H. Torrey noted visitors bypassed the Catskills entirely for the Adirondacks. The founding of the Catskill Mountain 3500 Club in 1962 - a peak-bagging organization requiring summits of the range's 35 highest mountains - finally gave the hiking community a voice and an identity.

Four designated wilderness areas anchor the park's wildest terrain: Slide Mountain and Big Indian-Beaverkill in Ulster County, Indian Head and West Kill in Greene County. In these areas, no chainsaws may operate without written permission from the DEC commissioner. No vehicles may enter except in dire emergencies. Trails are single-track, avoiding old logging roads. Some 400 black bears roam these forests alongside bobcats, fishers, and mink. The summits of the High Peaks harbor boreal forests that serve as summer habitat for Bicknell's thrush, a rare species whose 1999 designation as a Bird Conservation Area was the first such action in either of New York's Forest Preserves. Slide Mountain, at 4,180 feet the range's highest point, still draws hikers up the trail first built at public expense in 1892 - for the princely sum of $250.

From altitude, the Catskills reveal their essential character: rounded summits densely cloaked in hardwood and spruce, cut by deep valleys where streams run clear to feed the city's reservoirs far below. The mountains lack the jagged drama of the Rockies or the stark granite of the Adirondack High Peaks, but their beauty is in their continuity - ridge after forested ridge rolling westward from the Hudson Valley escarpment. The Belleayre Mountain Ski Center, authorized by a 1948 amendment to Article 14, cuts a visible swath through the forest canopy. The reservoirs - Ashokan, Pepacton, Neversink, Rondout - glint like silver plates set among the ridges. Half a million visitors come each year to hike, fish, ski, and camp in a park that owes its existence not to grand conservation ideals but to a tax dodge that became a constitutional guarantee.