The Tennessee and Cumberland Rivers are master rivers of the Interior Lower Plateaus. Their origins are very ancient. The course of the Cumberland River and the north-tending segment of the Tennessee Valley probably predate the Mississippi Embayment. Both reach the head of the Mississippi Embayment at the structural junction of the Reelfoot Rift and its arms which split toward St. Louis and southwestern Indiana. Forts Henry and Donelson were placed in strategic locations created by the enviroment that created these rivers. Man has used these rivers for transportation and life giving water from pre-historic to present times. Controlling transportation on the two rivers was critical to the success of both armies during the Civil War. Controlling the rivers is just as importand today for transtortation, flood control, and generating electricty. All of the environmental factors and the influence of man have and will continue to alter this area. Studying and understanding the process is a major undertaking by the staff of Fort Donelson National Battlefield and the National Park Service.