Thomas Mill Covered Bridge spans Wissahickon Creek in Wissahickon Valley Park in northwest Philadelphia. Built in 1855 as a single-span Howe truss, it is Philadelphia’s only surviving covered bridge and is noted as the only covered bridge in a major American city. Its enclosed wooden form preserves a rare example of a once-common bridge type that largely vanished from urban settings. Renovated in 1939 by the Works Progress Administration and again in 2000 by the city, it now serves pedestrians and bicyclists. Its importance is recognized by its 1980 listing on the National Register of Historic Places and as a contributing property in the Chestnut Hill Historic District.