The Union Canal was a towpath canal that existed in southeastern Pennsylvania in the United States during the 19th century. First proposed in 1690 to connect Philadelphia with the Susquehanna River, it ran approximately 75 mi (120 km) from Middletown on the Susquehanna below Harrisburg to Reading on the Schuylkill River. Although construction began in 1792 during the George Washington Administration, financial difficulties delayed its completion until 1828. Called the "Golden Link," it provided a critical early transportation route for the shipment of anthracite coal and lumber eastward to Philadelphia. Although closed in the 1880s, remnants of the canal remain, most notably the Union Canal Tunnel, a hand-built engineering marvel that is the oldest existing transportation tunnel in the United States.