In 1942, Ayerst McKenna & Harrison Ltd, founded in 1925, erected a plant for the production of pharmaceutical products on du Nord Road (now Marcel-Laurin boulevard) in Saint-Laurent. The company experienced staggering growth, since over a period of a few short months seven more buildings were built on land purchased by Ayerst. The company specializes among other things in the production of penicillin, hormones and biological and bacteriological preparations.

In 1984 the company decided to focus its research efforts in the United States due to the lack of protection offered by Canadian pharmaceutical patent laws. After changing its name to Wyeth in 2002, the company is now one of the most economically viable in Saint-Laurent, with over 950 employees. Furthermore, it is Canada's biggest exporter of pharmaceutical products.

Inside Wyeth plant