Down the eastern seaboard of the United States the Appalachians present a barrier to commercial transportation. Through this mountain wall the state of New York has a convenient passage in the Mohawk Valley. Pennsylvania, however, has no such gateway to the western part of the State, and beyond. Even the Juniata Valley, which penetrates far into the interior, is brought up short by the huge, unbroken mass of Allegheny Mountain.

In colonial days, to overcome the Appalachian barrier, traders drove trains of pack horses (each carrying a load of some two hundred pounds) up and down the mountain ridges; but the cost of transporting goods over such heights, even after the Indian trails which the pack trains followed had been widened to accommodate wagons, was prohibitive of commerce on any extended scale.

Nature herself, however, had provided a partial solution to the problem she had thus created. Great rivers, the Delaware, Susquehanna, and Allegheny, pierced the mountains, range after range (except for the Allegheny Mountain), by way of gorges known locally as "water gaps"; and in the valleys between these ranges flowed countless navigable tributaries.

From the earliest days of the Province of Pennsylvania, plans were studied for encouraging trade by means of waterways. William Penn, the Founder, as early as 1690 dreamed of connecting Delaware River traffic with the Susquehanna River. His thought was to build a canal to follow the upstream course of Tulpehocken Creek from its mouth on the Schuylkill River and the downstream course of the Swatara to its mouth on the Susquehanna. Such a canal would bind the Delaware, Schuylkill, and Susquehanna rivers into one great system of transportation.

A century was to pass, however, before Pennsylvania had its first artificial waterway. In 1797 the Conewago Canal, built on the west bank of the Susquehanna below York Haven to enable boats to avoid the rocks and rapids of the Conewago Falls, was declared operable by the state. Its purpose was to link river traffic safely with Columbia and with the turnpike which ran from that town to Philadelphia.

The great spur to Pennsylvania canal building came from the example of the Erie Canal three decades later. As that New York state project went forward between 1817 and 1825, Pennsylvania stock companies improved navigation on the Schuylkill; and the Union Canal Company carried into final effect, in 1828, Penn's idea of joining the Schuylkill with the Susquehanna by a canal along Tulpehocken and Swatara Creeks, thus connecting Middletown with Philadelphia by water.