Public Markets Limited (PML) was incorporated In 1911 by the Manitoba Government in order to provide Manitoba livestock producers with a market-place to accommodate this growing industry. A 137-acre [or 232- acre] site located on Marion Street in St. Boniface was purchased by the City of Winnipeg. In the land title reocords, this areas was referred to as the ‘Roman Catholic Mission Property’. On August 14, 1913, the Marion Street facility, with its stock yards and packing house facility, was officially opened by Premier Sir Rodmond Roblin. For the next seventy-five years, this facility, known as the Union Stock Yards, not only provided the City of St. Boniface with its largest single source of employers but became a vital cog in Manitoba's agricultural economy.

According to the Manitoba Historical Society, "An agreement was made with three main railroads, the Canadian Northern Railway (CNR), Canadian Pacific Railway (CPR), and Grand Trunk Pacific Railway (GTP), all of whom wanted service access to the sites... [The] PML was financed with a capital stock of $1.5 million and 10,000 shares of $100. Each railroad company was allotted 3,333 shares and one directorship in the PML. The railroads retained collective ownership of PML while the public was guaranteed a voice, and ability to affect prices, with several provincially-appointed directors to represent local producers and the public interest."

The livestock business in Manitoba owes its origins to the great cattle drives in the Southwestern United States. The Dodge City/Western Trail led up into Alberta where it hooked up with the newly completed Canadian National Railway. Cattle were loaded on to freight cars and shipped to the markets in Eastern Canada. Along the way the trains stopped off in Winnipeg to water and feed the cattle, giving rise to Manitoba's livestock industry. Winnipeg's first stock yard was located in the Weston area but space constraints and easier access to the rail lines necessitated the move to St. Boniface. The Union Stock Yards were the largest of their kind in Canada. The yard had its own private well essential in providing the endless stream of water required.

In 1925, Canada Packers opened a meat processing plant next to the yard, thirteen years later they were joined by Swift. World War II brought unprecedented growth to the packing industry as Canada supplied meat for the troops overseas. The yards represented a large cross-section of livestock interests. Within its structure were numerous salesmen, buyers, producers and employees of the trade and yard company. The Canada Department of Agriculture also provided two essential services. Veterinarians performed health inspections and a daily market report was prepared to inform the industry on livestock values and prices. Truck and brand inspections were carried out by representatives of the provincial governments. The market had its own Livestock Exchange to supervise trading and its membership included buyers for all kinds of stock as well as bonded commission firms and dealers.

The livestock received and sold at Union Stock Yards came from all three prairie provinces, destined for the local market, Eastern Canada, or under favourable exchange and trading conditions, the United States. The principal requirement locally was to provide slaughter cattle for the processing plants. However, under good weather and feed conditions there was a significant turnover of cattle back into the Manitoba feed lots for finishing. The Eastern Canada market was constant year-round with upwards of 300,000 cattle and calves shipped annually. The yard was also the largest exporter of feeder cattle in Canada with steady sales to Iowa, Minnesota, and Nebraska.

Failure to keep up with technological advancements and the advent of refrigerated trucks conspired to end the Union Stock Yards dominance of the industry. Trucks took over as the principal means of beef shipping with the completion of the Trans Canada Highway in 1955. The meat packing industry began to move closer to the source of its product as plants in Alberta supplanted Winnipeg processors. Manitoba hog processing still remains a viable industry but the Union Stock Yards, Canada Packers and Swift beef processing plants had outlived their usefulness by 1990. The Swift plant was demolished in 1994.