To learn more about Labor Day and labor issues in South Dakota, check out the Albert J. Maag papers in the Archives and Special Collections.
Albert J. Maag (1891-1965) was the president of the South Dakota State Federation of Labor. This collection contains correspondence, minutes of the annual AFL conventions, and yearbooks of the federation, plus much, much more. It even has a folder on Labor Day. Most of the collection dates from 1928 through 1964.
Image from the Albert J. Maag papers.