was part of the Flood Control Act passed by Congress on December 22, 1944. The final paragraph of S.D. 247 states that the plan “will secure the maximum benefits for flood control, irrigation, navigation, power, domestic, industrial and sanitary water supply, wildlife, and recreation.”

The first public mainstem dam on the Missouri River pre-dated Pick– Sloan. The Fort Peck Dam was built in Montana in the 1930s as a Works Progress Administration project promoted by President Franklin D. Roosevelt. The five mainstem dams downstream of Fort Peck and dozens of tributary dams were constructed as part of Pick–Sloan. Missouri River mainstem reservoirs behind Fort Peck Dam in Montana (Fort Peck Lake), Garrison Dam in North Dakota (Lake Sakakawea), and Oahe Dam in South Dakota (Lake Oahe) are three of the nation’s five largest human-made lakes (only Lake Mead and Lake Powell, both on the Colorado River, are larger). Although the river and its tributaries are extensively controlled by dams, channel modifications, and bank stabilization projects, the Missouri River is still subject to flooding, especially on the lower river. Like most major U.S. water projects, the Missouri River dams were authorized and built prior to the passage of modern environmental statutes such as the National Environmental Policy Act (1969) and the Endangered Species Act (1973), but not the Fish and Wildlife Coordination Act of 1934, which predates most of the dams.

The Corps of Engineers constructed and operates six of the Missouri’s seven mainstem dams (the Bureau of Reclamation constructed and operates Canyon Ferry dam, the comparatively small mainstem dam farthest upstream). Operations of these six dams are guided by the Corps’ 1979 Missouri River Main Stem Reservoir System Reservoir Regulation Manual, usually referred to as the “Master Manual.” A severe drought across the basin in the late 1980s and early 1990s focused national attention on the tensions and conflicts among management objectives and competing beneficiaries. During this drought, upper basin reservoirs were drawn down (reducing benefits for recreation and tourism), and lower basin states experienced disruptions to navigation and water supplies.

The pronounced drought of 1988–1992 affected most parts of the Missouri River basin. Negative impacts on reservoir-based recreation (upstream), on navigation (downstream), and on threatened and endangered species were so severe that in 1989, Congress directed the Corps to review the Master Manual. That review was conducted according to guidelines in the National Environmental Policy Act (NEPA), which requires the Corps to conduct an environmental impact statement (EIS) regarding changes in dam operations. As early as August 1994, the U.S. Fish and Wildlife Service (USFWS) issued jeopardy opinions (which state that a proposed action will jeopardize the existence of a threatened or endangered species) regarding operation of the Missouri River dams and the threat to federally