Wissahickon Valley Park includes the Wissahickon Creek gorge, designated a National Natural Landmark in 1964, a distinctive Philadelphia landscape carved through Wissahickon Schist bedrock with steep wooded hillsides, historic structures, sculptures, and Philadelphia's only remaining covered bridge. Its trail system has over 50 miles of biking, hiking, and equestrian trails and is a designated National Recreational Trail. Nearby are the Toleration Statue, a gift from John Welsh depicting William Penn and created by Herman Kirn in 1883; the Walnut Lane Bridge, whose center arch made it the highest and longest bridge of its kind in the world when it opened in 1908 and which connects Germantown and Roxborough across the creek; the Thomas Mansion, built in 1869 as George Clifford Thomas's house and donated to Fairmount Park after his death in 1907; Historic Rittenhousetown, established in 1690 by William Rittenhouse as the site of the first paper mill in North America and the birthplace of David Rittenhouse; and the Henry Avenue Bridge, designed in 1927 by Paul Philippe Cret with Frank M. Masters and dedicated to men and women of Philadelphia's northwest neighborhoods who served in World War I. The Wissahickon Creek Watershed covers 64 square miles in Philadelphia and Montgomery counties, and runoff from its surfaces can carry pollutants into the creek, a major source of Philadelphia's drinking water. The Fairmount Park Commission was established in 1868 to help ensure clean drinking water, and parkland vegetation continues to filter stormwater, reduce erosion, cool creeks, and improve habitat for fish and other aquatic organisms.
