Final answer:
Labor gains made during WWI and the Progressive Era were overturned in the 1920s due to factors such as the language barriers faced by immigrants, reluctance of farmers and African Americans to join unions, and a decline in the need for unskilled labor.
Step-by-step explanation:
The gains made for labor during WWI and the Progressive Era were overturned during the 1920s due to several factors. One reason was the influx of immigrants who faced language barriers and difficult living conditions, making it difficult to organize into unions. Additionally, many farmers and African Americans were reluctant to join unions. The decline in the need for unskilled labor, conservative political climate, and prosperity that led to low unemployment all contributed to the decline in labor activism.