In the early years of the twentieth century the AMCBW experienced some success, however the union was very divided and unorganized, and lost two major strikes in 1904 and 1921–1922.
[3] The PWOC was very successful in recruiting African American workers, who dominated the packinghouses in Chicago and Kansas City.
[1] It was also successful in recruiting rural white workers, and succeeded in overcoming ethnic and racial antagonisms that had plagued similar, previous efforts.
Active in both black and white neighborhoods, the PWOC functioned as an important social and cultural institution in addition to its primary role as a union.
In the 1940s, the UPWA won nationwide contracts with companies including all members of the "Big Four" of meatpacking: Armour, Swift, Wilson, and Cudahy.
[8] In 1950, the UPWA created an Anti-Discrimination Department, dedicated to ending racial discrimination in meat packing plants and working against segregation in local communities.
[6] In the 1950s and 1960s, the UPWA was at the forefront of union support for the Civil Rights Movement and was a strong ally of Martin Luther King Jr.
By establishing plants in areas closer to animal populations, and by introducing new technologies that required less skill, the "Big Three" drove many older companies out of business.