The oldest, and for a long time the longest, tunnel in the United States completed William Penn's idea of linking the Susquehanna and Delaware rivers. Unfortunately, soon after it was completed railroads would supplant canals for moving heavy materials. Dug through the ridge dividing the waters of Quittapahilla Creek and Clark's Run, the tunnel was originally 729 feet long. Its route was laid out in 1762 by Philadelphia scientist and mathematician David Rittenhouse assisted by the son of the College of Philadelphia's provost William Smith. First chartered as the Schuylkill and Susquehanna Canal Co., construction began in 1792 under the direction of William Weston, an English engineer. Several miles of the easy parts of the canal were dug and five locks were built between Myerstown and Lebanon before financial difficulties caused the work to cease. It was this area that President George Washington visited in 1793. Reorganized in 1811 as the Union Canal Company of Pennsylvania with Samuel Mifflin as president, work began again in 1821 under the direction of chief engineer Canvass White, of Erie Canal fame, with Simeon Guilford as his assistant. The canal was finally completed in 1828. A branch canal was finished in 1832 reaching from a pumping station at the village now called Union Water Works north to Pine Grove to tap the coalfields and supply muchneeded water for the otherwise dry Summit Level. Despite a cost in excess of six million dollars, the 102 locks of the canal could not accommodate the larger boats from the Pennsylvania and Schuylkill canals, necessitating enlargement in the 1850s. A flood in June 1862 devastated the canal from Pine Grove to Middletown. Costly repairs, continual water supply problems, and the completion of the Lebanon Valley Railroad in 1857 from Reading to Harrisburg each served to reduce revenues, leading to the closing of Union Canal in 1885. Designated a National Historic Civil Engineering Landmark in 1970, this tunnel is the oldest existing transportation tunnel in the United States. In the early 1930s, workers from the Civil Works Administration restored the tunnel and a portion is used for summer canal boat rides.