A covered bridge once crossed both the canal and the Schuylkill River about one hundred yards north of the present bridge that carries State Street into Tilden Township, and in the fall and winter its east and west foundations are plainly visible. The Schuylkill Navigation Canal was unique in its construction, extending roughly one hundred and ten miles from Schuylkill Haven to Philadelphia, with about one half of it navigable water in "slack water" pools created by damming the river, including the system's highest dam, the twenty-nine-foot-plus Big Blue Mountain Dam at Kernsville, while the remainder consisted of actual canal and locking systems.