History & Culture - Potomac Heritage National Scenic Trail (U.S. National Park Service) (2024)

The theme of an east-west corridor links the history, transportation and technology of the Potomac River corridor. Prior to the European invasion, land transportation in the Potomac region was largely by trail, usually the improved trace of a game trail. Large mammals, especially bison and elk during historic times, picked routes that used the least energy and, over the years, the passage of animals engraved trails in the landscape. People followed these trails and the resulting paths became the established routes of travel.

Transportation by waterway was unreliable at best. Whenever paddlers encountered an obstruction they would have to carry their crafts around the obstructions. But as General Washington recognized, the Potomac represented more than an avenue west--it also represented resources and water power. The River has provided a rich fisheries resource, remarked upon by Captain Henry Fleet in 1631. Washington harvested the river to feed his establishment fish, both fresh and salt, to sell and to fertilize his fields. The shad population in the River may be taken as an example of a fairly typical change in abundance overtime. Washington harvested a seemingly unlimited population of shad and, in the 1832 harvest, 22,500,000 were taken. A century of overfishing, obstacles to upstream migration, and pollution have resulted in reducing the shad population to the status of threatened. Today, however, American shad reintroduction is described as a success story.

European colonists recognized the vast potential of waterpower by adopting water laws, including mill seat rights, as some of their first legislation. As long as the Europeans remained confined to the Tidewater, there were very few sites with enough feet of fall to power a water mill. Wind and tidal mills predominated during this period, but as settlement expanded into the Piedmont mill-seats became an important aspect of land grants. The individual mill evolved in two ways: Many started as saw mills and produced lumber until the area was cleared; and either seasonally or sequentially, they were used to mill grain, plaster, bone, wool, paper as well as used for cutting stone.

For example, the recent efforts to bring back American shad, a species once economically important, have been successful, but only to a point. The numbers of shad are growing but it is still unlawful to catch and keep shad.

Today there is greater interest in ecology than ever before, but the idea lingers that ecology is a subject important only in the biological sciences. Other groups do include the effects of humans as an innate part of ecology; in the social sciences, however, ecology is viewed as if humanity were the only agent responsible for change.

The effects of time, as another major factor in ecological change, is consistently minimized or ignored by many. In 1886, William Morris Davis of the Pennsylvania Geological Survey published a paper called "Rivers and Valleys of Pennsylvania"; with a few corrections, this paper is still applicable today and describes four major physical factors that shape rivers: 1) the formation of wind and water gaps by erosion; 2) headwater migration of divides; 3) stream piracy; and 4) adjustments to stream structure.

Scientists think that many millions of years ago a super continent, called Pangea, began to break apart to form the modern continents. The topographic changes occurring after the continental split have resulted in the present Chesapeake Bay and Potomac River basin:

• A huge meteorite impacted the earth at what is today the mouth of the Chesapeake Bay, creating a giant crater and further affecting the direction of flow of the proto-rivers (rivers before the Potomac's existence).

• The westward erosion of the headwaters of the ancient Potomac captured other drainage systems, such as the Shenandoah, and thus increased the size of the basin.

• The Potomac River's flow and flooding wore down the heights of the uplifting plateau, resulting in sedimentation and water and wind gaps--spaces eroded from mountains; examples include the Gap in the Blue Ridge where the Potomac and the Shenandoah rivers converge.