From the early 1960s through the mid-1970s, Levi Strauss experienced significant growth in its business as the more casual look of the 1960s and 1970s ushered in the "blue jeans craze" and served as a catalyst for the brand. Levi's, under the leadership of Walter Haas, Peter Haas Sr., Paul Glasco and George P. Simpkins Sr., expanded the firm's clothing line by adding new fashions and models, including stone-washed jeans through the acquisition of Great Western Garment Co. (GWG), a Canadian clothing manufacturer acquired by Levi's. The acquisition lead to the introduction of the modern "stone washing" technique, still in use by Levi Strauss. Simpkins is credited with the company's record-paced expansion of its manufacturing capacity from 16 plants to more than 63 plants in the United States from 1964 to 1974 and 23 overseas. Levi's' expansion under Simpkins was accomplished without a single unionized employee as a result of Levi's' and the Haas family's strong stance on human rights and Simpkins' use of "pay for performance" manufacturing from the sewing machine operator level up. As a result, Levi's' plants were perhaps the highest performing, best organized and cleanest textile facilities of their time.