The link between healthy forests and watersheds and healthy streamflow and quality water is universally recognized. The major rivers of the USA originate in the forested mountains of the western and eastern USA and the glaciated regions of the Lake States and Great Plains and produce almost two-thirds of the nation’s clean water supply. Original logging and mismanagement of upstream forested watersheds often resulted in degradation of land and water resources and adversely impacted aquatic and human populations. During the 30-year period, between the 1930s and 1960s, experimental forests, ranges, and watersheds were established on national forests and adjacent lands to study the impacts of land conditions on water yield, stormflow, water quality, and nutrient cycling. While the impact of sustained timber production was an original research focus, current efforts include research on nutrient cycling, carbon sequestration, climate change, fire effects, and the impacts of insects and diseases. The experimental forest network of long-term meteorological and biological records is invaluable for evaluations of potential climate change and its consequences on the forests and water resources. This chapter reviews hydrology and watershed management research at a sample of experimental forests and areas from throughout the USA. The chapter includes studies conducted in the forests near the Fort Valley Experimental Forest and on the Sierra Ancha Experimental Forest in Arizona, on the Fraser Experimental Forest in Colorado, and the H.J. Andrews Experimental Forest in Oregon. In the East, research at the Coweeta Hydrologic Laboratory in North Carolina, the Hubbard Brook Experimental Forest in New Hampshire, and the Marcell Experimental Forest in Minnesota is reviewed.