The D-H Canal was designated a National Historic Landmark in 1968. In 1999, the High Falls locks--16 through 20--were cleared and refurbished (to the extent possible). These five locks were built in 1847, as part of a new route designed to accommodate increased traffic and larger canal boats. This section also included a loading quay, still visible just past lock 16. The canal locks were constructed of Shawangunk conglomerate, an indigenous stone. Each lock measured 90’ long, 15’ wide, and 15’ deep, and provided an average change in elevation of 12.6’.