Tree Rock, a small limber pine growing from a crack in a boulder of Precambrian pink Sherman granite on Sherman Mountain, has fascinated travelers since the first Union Pacific Railroad trains passed it. According to local tradition, builders of the original railroad diverted the tracks slightly to pass by the tree as they laid rails across Sherman Mountain in 1867-69, and trains stopped there while locomotive firemen gave the tree a drink from their water buckets. After the railroad moved several miles south in 1901, the abandoned grade became a wagon road. The Lincoln Highway, created after the Lincoln Highway Association formed in 1913 to establish a continuous improved highway from the Atlantic to the Pacific, passed right by Tree Rock, as did U.S. 30 in the 1920s and Interstate 80 in the 1960s. Near the 8,835-foot Sherman Summit, the highest point on the Lincoln, the site offered westbound easterners striking mountain views, yet many especially noticed the little tree, which became a favored subject of early postcards and photographs and remains so. The tree is a somewhat stunted and twisted limber pine, a species common in this area where ponderosa and limber pines dominate the landscape; its age is unknown, though limber pines can live as long as 2,000 years.