In 1956 the U.S. Army Corps of Engineers was directed by Congress to undertake a Basinwide study to develop a plan for flood control and the conservation of water resources and related land resources. The emphasis in this assignment was upon a full long-term functional solution for the Basin's water problems in feasible economic and technological terms. In carrying it out, the Army enlisted the aid of other Federal agencies, and their _Potomac River Basin Report_, published in nine volumes in 1963, presented the study's results and a plan for Basin water development to meet needs to the year 2010. It is a monumental piece of work to which anyone concerned with the Basin henceforth will have to refer, because of the completeness with which it examines the Potomac water resource and the careful technical knowledge it brings to bear on Potomac problems. However, the plan it presents--including recommendations for sixteen major multipurpose reservoirs on the Potomac and its tributaries--would bring about a massive and permanent revision of the free-flowing stream system and would inundate much valley land. It aroused articulate opposition at local, state, and Congressional levels, a good deal of which was focused on the key Seneca dam on the Potomac main stem just above Washington--an area where earlier single proposals for dams, first at Great Falls and then at River Bend, had provoked similar resistance. Clearly enough, a powerful continuing body of opinion cares about something more than strictly functional values along the Potomac and in its Basin. It is a long-settled region, whose natives generally cherish what they have in the way of scenic and historic amenities. It is the part-time home of many influential lawmakers, who concern themselves about its beauty and well-being. And together with the national capital at the core of its metropolis, it is the vacation goal of millions of American tourists from elsewhere each year, who go home aware not only of monuments and marble halls of state but of crucial Civil War battlefields, dark mountain ridges overlooking classic river valleys, rolling Piedmont estates, and the wooded headlands of Virginia and Maryland that recede behind one another into haze as one looks down the estuary in summertime.