The deep ravines, irregular ridges, and rocky slopes of the Catskill Mountains long remained wild and desolate, with small settlements appearing in mountain valleys before the American Revolution and population growing steadily after the war as New Englanders moved into the higher areas they called the "cold lands." The Ulster and Delaware Turnpike was begun in 1802 to connect Kingston and Walton through mountain passes later used by present highways, and after 1875 the Ulster and Delaware Railroad, later part of the New York Central system, wound from Kingston to Oneonta. Timber and water power made lumbering the principal occupation, while hemlock stands supplied bark for tanning leather, and furniture makers, hoop shavers, bluestone quarrymen, and glass blowers also used the area's resources. Catskill vistas attracted many artists, and Washington Irving and John Burroughs wrote about the surroundings. The mountains also became famous as a resort area, and in 1904 the State established the Forest Preserve to safeguard the natural resources forever. Shandaken Tunnel, 18 miles long, was dug to connect Schoharie Reservoir with Esopus Creek to feed the Asokan Reservoir, a source of water for New York City since 1915.