[1] The park made up of 20.5 hectares of green space consisting of the greenery-covered Rosehill Reservoir and the entirety of the Vale of Avoca with its system of trails.

The area occupied by David A. Balfour Park has a long history prior to the colonization and the formation of Canada where it was an important hunting ground of the indigenous peoples, specifically the Mississaugas who referred to it as mishkodae (lit.

[5] During World War II, a fence was put up around the periphery of the open reservoir to protect the water supply from being sabotaged.

Post-war, the decision was made to deepen and cover the reservoir to increase its capacity, as well as to maintain the sanitation of the water from human pollution and animal contamination.

As consolation to the nearby residents in losing a well loved water feature in their neighbourhood, the city agreed to include several concrete lined ponds on the top of the enclosed reservoir.