As the Wisconsinan Ice-Age glaciers finally retreated about 10,000 years ago, their meltwaters formed an enormous lake, called Lake Agassiz, that stretched across southern and central Manitoba and into Saskatchewan and Northwest Ontario, reaching depths up to 200 metres. In southern Manitoba, it deposited thick layers of silt that would contribute to the region’s great soil fertility.

About 8500 years ago, the last significant portion of the lake drained into Hudson Bay. However, major remnants such as Lakes Winnipeg, Manitoba and Winnipegosis persisted. As the land surface slowly rebounds from the glaciers’ weight, these lakes will continue to alter in depth and shape. With the retreat of the glaciers and their meltwater lakes, plant and animal life began to re-establish, leading eventually to the first human influx of the region ^_ the aboriginal peoples.

Following first operation of Pinawa Generating Station in 1906, rapid further development of the Winnipeg River’s hydro-electric potential followed. By 1954, six further generating stations had been developed. In order of construction, they are: Pointe du Bois (1911, capacity 72 MW), Great Falls (1923, 132 MW), Slave Falls (1931, 68 MW), Seven Sisters (1931, 150 MW), Pine Falls (1951, 82 MW) and McArthur Falls (1954, 56 MW). Together, these stations can generate a total of 560 MW, about 13% of the electricity produced by the province.

Manitoba’s population had grown sufficiently by 1900 to justify development of the province’s hydro-electric potential. The first dam constructed on the Winnipeg River system and was called Pinawa Generating Station (G.S.). Pinawa G.S. began delivering electricity in 1906, initially 7.5 million watts ("megawatts" or MW), which was later increased to 23 MW. It operated until 1951, when it was finally decommissioned.

Today, the ruins of Pinawa G.S. and its adjacent townsite are a Provincial Heritage Site. Now affectionately known as "Old Pinawa" and located about 10 kilometres from present-day Pinawa, it is a popular destination for many summer activities.

Present-day Pinawa exists because of a decision taken in the late 1950s by Atomic Energy of Canada Limited (AECL) ^_ the Federal Government of Canada Crown Company responsible for the development of the peaceful uses of nuclear energy ^_ to establish a new research laboratory in eastern Manitoba. Known originally as the Whiteshell Nuclear Research Establishment (WNRE), the laboratory was constructed from 1960-1965, simultaneously with the new townsite of Pinawa to house many of its employees.

The principal research facility at WNRE was an innovative oil-cooled reactor design known as "WR-1", which was used to investigate many aspects of nuclear science. Producing up to 55 MW of heat, WR-1 operated for nearly 20 years until it was eventually shut down in 1985. At the height of its research activities, WNRE employed over 1200 people, the major areas of investigation being nuclear-reactor and reactor-materials research, reactor-safety studies, nuclear-waste management and ecological studies.

In 1998, due to financial constraints, AECL decided to gradually wind down its research activities at WNRE and to decommission much of its facilities at the site. As new uses for the site and its remaining facilities are being investigated, the legacy of the continuing existence of the beautiful townsite of present-day Pinawa and its lifestyle continues.