The Adirondack Mountains are a vast New York wilderness of rocky peaks, sheer cliffs, narrow valleys, wooded slopes, and sparkling lakes. Forty three mountains rise four thousand feet or higher, and Mount Marcy, at five thousand three hundred forty four feet, is the highest; near its summit is Lake Tear-of-the-Clouds, the source of the Hudson River. The name Adirondack, meaning "tree-eater," was given derisively by the Iroquois to some of their Algonkian enemies. Long used as Indian hunting territory, the region was not penetrated by white men until the late 18th century. Mining began at the end of that century, producing iron, zinc, titanium, talc, and garnet, while the forests supplied timber through the 19th century and the first decades of the 20th. Concern over the destruction of these forests led New York to establish the Forest Preserve in 1885, and Adirondack Park now includes more than two million state-owned acres. After 1871, railroad construction transformed remote forest retreats into popular summer resorts, and automobile highways in the 20th century made the area's rugged beauty accessible to all.