ABSTRACTMeltwater from a receding glacier created the Des Moines River in central Iowa 12,000-14,000 years ago. Over the ensuing centuries the river overflowed its banks, flooding the plains then receding, meandering across the landscape. During the first century of statehood Iowa river towns experienced loss of life and property damage from repeated flooding. Federal officials determined that a dam was needed on the Des Moines River. The United States Army Corps of Engineers (USACE) began construction in 1965 and completed the project in 1977. Although the USACE carefully planned and evaluated every aspect of the project, significant obstacles arose, and community opposition highlighted the plan’s shortcomings. Nevertheless, the project went forward at least in part because ordinary Iowans believed they could not effectively fight the government. During the first phases of the plan local citizens with Cold War concerns yielded to federal officials and their use of eminent domain regulations. As the project neared completion in the 1970s, the treasured Ledges State Park faced the threat of sustained flooding due to the future Saylorville Dam. While the federally staffed Corps of Engineers led the earth moving project, the federal government also enacted environmental protection laws that activists used to force negotiations and alter the parameters of the original master plan. Environmental activists in Iowa used provisions from the legislation that required the USACE to complete an Environmental Impact Statement about the Saylorville Reservoir project. The time required to draft the statement paused construction and afforded activists more time to negotiate with officials about issues of concern. From Cold War convictions to expressions of environmentalism, the people of Iowa moved through the decades of the mid-twentieth century, both reacting to local pressures and reflecting national concerns.