The USWA started to organize in Saskatchewan in the 1950s. The membership was mainly located in Regina at IPSCO, Dominion Bridge, Westeel, Westank Willock, and Federal Pioneer Electric. In 1968, a fierce competition occurred amongst Oil, Chemical and Atomic Workers (OCAW), Tunnel and Rock Workers Union, Local 168, United Stone and Allied Product Workers, and USWA to represent the miners at the Duval potash mine near Saskatoon. The Steelworkers, spearheaded by Terry Stevens, a steelworker organizer from Winnipeg, were successful in organizing Duval Corp. (PCS Cory Local 7458), Cominco (Agrium Local 7552), Allan Potash (PCS Allan Local 7689), and Central Canada Potash (IMC, Local 7656) between 1968 and 1971. Workers at Potash Company of America (PCS Patience Lake Local 189) became Steelworkers in 1972 when their former union, United Stone and Allied Product Workers Local 189, merged with USWA.
Collective bargaining in the industry was very difficult; lengthy strikes took place at Cominco in 1972, 1979 and 1995, at Duval in 1973 and 1975, and at PCA in 1975. The Steelworkers supported the public ownership of the potash industry and the formation of the Potash Company of Saskatchewan brought in by the Allan Blakeney government. Bargaining at the new publicly owned mines of PCS Cory (Duval) and PCS Allan (Allan Potash Mines) greatly improved union members' benefits. These included paid sick days, long-term disability, life insurance, pensions, vision and dental coverage for the employees and their family members, as well as a new job evaluation program - known as Co-operative Wage Study (CWS) - an employee and family assistance program, and double time for overtime. Steelworkers were also successful in obtaining these benefits for their members in the non-publicly owned PCS mines.
Steelworkers were the first to organize a branch of the Toronto Dominion Bank; Develcon, a high-tech electronics firm; the office staff of the Saskatoon law firm, Mitchell, Taylor, Romanow and Ching; and the office employees of Saskatchewan Mutual Insurance.
The membership of the union has fluctuated over the years owing to mine and plant closures at Dominion Bridge, Great West Steel, Eldorado Nuclear, Westeel, Westank Willock and Federal Pioneer.
In September 2004, a merger between the International Woodworkers of Canada and USWA created the largest industrial union in western Canada, with a Saskatchewan membership of 4,500. The merged union has members in the manufacturing of steel, pipe, agricultural equipment, wood and allied products, among office and technical employees, as well as in uranium and potash mining and milling.