A river system draining the basin it has carved out over geological eons of time is one of the more meaningful units in nature, but within it there may be great variety. The Potomac starts as a multitude of diverse trickles and oozes in the high green places of Appalachia, where spruce forests and berry meadows and bogs know the tread of bear and deer, beaver and bobcat, hunter and hiker and logger. The clear cold streamlets formed there join together in their downward rush and form strong whitewater creeks and rivers slicing down through canyons and out into the troughs of the strikingly corrugated Ridge and Valley Province, growing ever larger by the process of union and addition.
The two main rivers formed thus are the North Branch, which collects a plenitude of troubles in its progress as we have seen, and the South Branch, which is treated more gently by the farmers and small townsmen who live along it, has no developed coal resources, and is a delightful fishing stream in a fine rural valley. Coming together at Old Town where Thomas Cresap took over a Shawnee site and set up a fortified headquarters in the upper Basin's legendary days, these two form the main stem of the river, which works across the Ridge and Valley washboard by intricate slicings and loopings that shape great bends among the forested hills. Deer and turkey outnumber people in most places there, and always alongside the river or not far away lie the towpath and the dry channel and the occasional stone locks and aqueducts of the old C. & O. Canal. Despite railroad competition and floods and all the other troubles, its barge traffic in coal and flour and whiskey and iron and limestone and other things was the focus of a whole roistering way of life from Washington to Cumberland in the 19th and early 20th centuries.
Collecting the water of pristine mountain tributaries like the Cacapon and growing as it goes, cleansing itself of the North Branch's load of trouble, the river finds its way at last out of the washboard and meanders among silver maples and great sycamores across the productive populated expanse of the Great Valley that runs athwart the whole Basin from north to south. The Potomac is in thickly historic country now as it flows under the contemplative eyes of fishermen and past old villages and the relics of generations of human activity going back before written records, for here and there the funnel shapes of stone Indian fishing weirs can still be seen at shallow places and the durable fragments of their way of life can be scratched up along high shores. Of many Civil War clashes in the valley, Antietam was the most crucial; the Potomac shaped Lee's strategy there, and still ripples across fords by which his troops came to that violent place and afterward escaped it.
At Harpers Ferry on the Valley's eastern edge, the river is reinforced by the waters of its greatest tributary, the Shenandoah, rolling north out of the limestone country that fed the gray armies till Sheridan put a stop to that. Then it rams through the high wall of the Blue Ridge and out of the Valley into the Piedmont, and still gathering strength from tributaries like the Monocacy, dotted with big islands and frequented by waterfowl and good fish, moves powerfully downcountry past further mists and layers of history to Great Falls and the rushing, crashing descent through the gorge to tidewater at the capital.
From there down it is, as we have seen, a different thing, an arm of the sea and a sluggish extension of the river, shading from fresh to salt, called a river still but neither river nor sea in its ways, affected rhythmically and obscurely by both of them and subject to its own complex laws as well. In Indian and Colonial times this estuary was the part of the river that counted most for men, because of the bounty that came from its waters, the fitness of its shores for farming, and its navigability for boats and ships in a region where land travel was laborious and whose colonists depended on commerce with a European homeland. Its shores and those of the big tributary embayments—"drowned rivers," they have been called—are thickly sprinkled with traces and remembrances of three and a half centuries' people and events. Mount Vernon, old Fort Washington, Gunston Hall on Mason Neck where quiet George Mason lived and thought ... Aquia Creek where George Brent took his Piscataway bride to live apart from the Marylanders, Potomac Creek where John Smith found the river's namesakes living and another wily captain later tricked Pocahontas into captivity, Port Tobacco and Nanjemoy with memories of brokenlegged Booth, Chotank that gave its name to a whole forgotten way of life, Nomini of the Carters, the Machodocs and the Wicomico and the Saint Mary's and the historic rest.... Some of the big creeks are silted in now with mud washed down off the land in the old days, but in the flatter country toward the Bay most of the larger ones are still pretty and useful harbors for pleasure boats and for the fleets of varied commercial craft that go out to gather the estuary's crabs, oysters, clams, perch, striped bass, shad, and other edible creatures, including even eels for the European market. From hillsides, mellow mansions look down on the water that used to be their highway to the outside world, some crumbling, others proudly maintained.
Aquatic life in the upper freshwater stretches has been somewhat diminished and changed by pollution and silt, by dredging and filling, and by other activity. Runs of spawning shad and herring and perch still arrive there in spring, fortunately a season when heavy river flow keeps oxygen levels high. Along the whole estuary there is an abundance of air-breathing creatures, most noticeably birds, that reflect the wealth in its waters. They are strikingly numerous in the marshes that occur here and there next to the open river but more commonly up the tributaries, perhaps the richest biological areas in the whole river. Herons and egrets, ducks and geese, coots and grebes, hawks and ospreys and even a few bald eagles—a stirring sight so near to Megalopolis—are among the larger birds that congregate to live directly or indirectly off the life in the water, dependent on it.
Productive, healthy in its lower reaches even if under the shadow of change, its fishery intelligently and effectively regulated after the destructive and bitter "oyster wars" that persisted up into the 1950's, the Potomac estuary offers over 230,000 acres of water and some 750 miles of shoreline for human use and enjoyment and for the sustenance of a complex and valuable segment of the natural world. It is a fitting culmination of the river system that feeds down into it.
Of the Basin's remaining scenic and natural and historic wealth, nearly all of it associated to some degree with a part of the river system, much has stayed intact or has come back to good condition, accidentally or by someone's forethought. Well over a million acres are in public ownership of some kind, about a fifth of this being dedicated primarily to scenic preservation and public enjoyment as parks and recreation areas. These range from the great recently authorized Spruce Knob-Seneca Rocks National Recreation Area in the Basin's western highlands and the spectacular narrow Shenandoah National Park along the Blue Ridge, to local and county parks of smaller size and special function. In and around metropolitan Washington, good sense and good will on the part of many people in years past has resulted in a fine assortment of parks in an area where they are most needed and used, though with urban expansion more are needed all the time.