Lehigh Gorge State Park occupies rugged forested terrain that extends for 30 miles along the Lehigh River. From the north to south the river drops 700 feet making it a prime whitewater rafting area. The gorge was the site of early timbering; a system of dams, locks, and canal segments that made the river navigable; and subsequent railroads. However, forests have returned, dams long since washed out, and an abandoned rail line has been converted to a bicycle trail. Today the steep slopes of the gorge are again forested, with oak dominating the south-facing exposures and hemlock forests on the northern exposures and in steep tributary ravines. The gorge contains a significant concentration of reptiles and amphibians including 33 species, two of which, timber rattlesnake and hognose snake, are classified by the Pennsylvania Natural Heritage Program. In addition the state threatened Allegheny woodrat is present at several locations in the gorge. No endangered, threatened or rare plants were found within the park, however a small population of a native orchid that is on the watch list is present. Non-native invasive plants are for the most part limited to edges along roads, rail lines, riverbanks, and sites of former settlements. The most widespread and abundant invasive plant is glossy buckthorn, a European shrub that has spread along the riverbanks and adjacent lower slopes from Port Jenkins south.