Once the edge of Lake Iroquois the site became an extraction site for aggregates (Sand and Gravel) sometime in the early 1960s. As extraction took place small sections of groundwater became exposed, which saturated the ground, making extraction difficult. The difficulties in harvesting led to the closure of the aggregate operation in the early 1980s. The site was then purchased by the former Municipality of Metropolitan Toronto in 1969 as part of a landfill site selection process. For a short time the north lands were operated as a land fill starting in 1978. The land fill operation was eventually shut down and all waste was removed from the site by 1997.

The Brock Lands property is comprised of 392 hectares (969 acres) of greenspace. The northern portion, (Brock North) abuts another TRCA owned greenspace area, the Rodar Property. The eastern boundary of the southern portion (Brock South) abuts the Greenwood Conservation Area. When combined, the total area of these properties is 689 hectares (1,704 acres).

The majority of the Brock Lands lie within the Lake Iroquois Plain, created approximately 12,500 years ago along the shores of the glacial Lake Iroquois. The shoreline forms the southern boundary of the South Slope and is comprised of mainly gravel and sands. Together the Brock Lands and Greenwood Conservation Area play a critical role as a complex network of recharge and discharge areas for regional groundwater. The Duffins watershed is one of the last watersheds in the TRCA jurisdiction to exhibit the characteristics of a typical rural watershed, due to minimal urbanization, large natural areas, the predominance of sandy soils, and a relatively large amount of forest cover.

Within the property is the confluence of two sensitive watercourses; Brougham Creek, and Spring Creek, both are considered coolwater streams . Brougham Creek contains salmonid species, such as Brook trout and historically it would have supported Redside dace , a provincially and federally endangered fish species, which has not been identified in recent years due to lack of fisheries survey; however habitat potential is high. Spring Creek has been identified as supporting a population of the endangered Redside dace.

The site is characterized by a complex mosaic of cedar-dominated forest habitat and open meadow habitat interspersed with fen-like wetlands and ponds, which are the outcome of the extensively modified landscape resulting from past land uses. On the site a total of 103 vertebrate fauna species have been recorded by TRCA, which includes 33 species of regional concern and two species of provincial Species at Risk. A few species found on the site which may be of interest include:

Redside Dace Photo credit: Erling Holm / © ROM	Bobolink Photo credit: Smithsonian National Zoological Park