These lands were owned by the Three Affiliated Tribes, and the territory "had been their home for perhaps more than a millennium.

The tribes gained remuneration, but lost 94% of their agricultural land[6]: 59–60 in 1947, when they were forced to accept $5,105,625. This amount was increased to $7.5 million in 1949, but it did not fully compensate them for the loss of their important farmlands, homes, towns, and graves. They had cultivated the bottomlands and were able to be largely self-sufficient.

The final settlement legislation denied the tribes' right to use the reservoir shoreline for traditional grazing, hunting, fishing or other purposes, including irrigation development and royalty rights on all subsurface minerals within the reservoir area.

Thus construction of Garrison Dam almost totally destroyed the traditional way of life for the Three Affiliated Tribes and made them much more dependent on the federal government

Hydropower turbines at Garrison Dam have an electric power generating nameplate capacity of 583.3 MW. Average production of 240 MW serves several hundred thousand customers.