Rattray Marsh Conservation Area, is 94 acres[1] of environmentally sensitive wetland situated along the shore of Lake Ontario in Canada.

It is found on the west side of Jack Darling Memorial Park and is located in the city of Mississauga within the Regional Municipality of Peel.

It is the last remaining lakefront marsh on the western end of Lake Ontario and is owned and managed by Credit Valley Conservation.

A treaty was signed between the Mississauga people and new settlers in 1805 for land from Etobicoke creek to Burlington Bay and other areas reaching up to the north of Dundas street.

In 1861, Harris H. Fudger purchased some of the land upon which he built his mansion overlooking the marsh and the property was named Barrymede Farm.

[2] Rattray permitted local residents to swim on his beach, walk along the edge of the lake, and also invited his bird-watcher friends to pursue their hobby.

A committee led by Ruth Hussey wrote a letter to the Premier asking to encourage the Parks Integration Board to support the preservation of the Rattray Estate.

Camping on Rattray estate was thought highly undesirable by conservationists because of the unique characteristics of the area and its role in providing a habitat for many species.

[2] After all the conversation efforts failed, Mr. Brockington, sole executor and trustee of Rattray estate released the land for sale.

[2] Late in the year 1963, at the hearing between pro-conservation group and the supporters of private development, it was evident that CVCA would not be able to acquire the land due to not having enough funds.

They sought the help of Nature Conservancy of Canada, a country-wide organization recently founded at the time, to raise the funds.

While the bulldozers were clearing the trees and flora for construction, an article was published by Bruce West in The Globe and Mail praising the conservation efforts for the marsh.

Following the popularity of that letter, Hussey formed a new citizens' committee and created a petition to be sent to Township to reconsider the purchase of what remained of the Rattray Estate.

Dennis Veal, the biologist who conducted the study, helped arouse awareness and support from the citizens for the remaining 56.7 acres essential for buffer zone.

[2] In 1972, a planning board meeting was held with representation from provincial government, naturalists, conservation organization, local citizens and Neiman.

After some negotiation with Neiman, and financial support from citizens, CVCA purchased the property and the Rattray Marsh Conservation Area was officially opened on October 5, 1975.

[1] The sediment built up affects the water quality and quantity that results in the increase of invasive plants and species such as Carp in the Rattray Marsh.

[7] In the beginning of 2013, CVC started a phased removal of excess sediment from marsh which resulted in more observation of species at risk like Least Bittern.

There are initiatives such as Low Impact Development and Greening Corporate Grounds that are pursued to help reduce sediment from surrounding areas and restore the marsh ecosystem.

[10] The variety of plants and natural food sources found in Rattray Marsh provides an important habitat for many species of birds.

The fish migration times in the marsh are often dependent on the operation of the shingle bar affected by the variation in water level.