In the late 1950s, the Thames River Flood Control acquired authority over West Thompson village through the process of eminent domain. Following the disastrous impact of the floods in the past twenty years, people became aware of the need for protection in the Quinebaug River Valley. In December of 1955, the temporary organization known as the Society of the Quinebaug was formed in order to discover the assistance they required. On January 26, 1956, the Quinebaug-French Rivers Manufacturers Association was organized and included approximately seventy-five businesses whose primary concerns existed in southern Massachusetts and northern Connecticut.

In 1962, government officials and the Army Corps of Engineers began construction of the dam and completed the project by 1965. The project required tremendous excavation work and the rerouting of several local roads. The entire village of West Thompson had to be destroyed in order for the new dam and the lake to be constructed. Only ten of the village’s buildings were relocated from the area while the rest were razed in the early 1960s. 

West Thompson resident Alice Ramsdell refused to surrender her home to the federal government, using a loaded firearm in an attempt to save the land that had belonged to her family for generations. Eventually, the Corps granted her permission to stay on her land until she passed away because the property lay just above the final waterline of the new lake. The Army Corps of Engineers kept one of the houses in West Thompson and use it as an office today.

The structure of the dam is very elaborate and thorough, the top of the dam including a concrete spillway, dam invert, spillway weir, and a graveled dike. The dam’s structure is designed to protect West Thompson, Mechanicsville, and Putnam along with other towns and villages that lie further down the river valley.

In 1977, it was estimated that the dam had already saved over $1,200,000 in damage. Also, as of 1977 the highest water level of the reservoir occurred in March of 1968 after a two day period of rainfall accumulating 3.8 inches of water and snow melt runoff. The reservoir measured up to 37.5 feet and reached 48% of its total capacity.