Final answer:
Labor unions indeed formed during the Progressive Era to advocate for workers' rights, making the statement true. The era contributed significantly to labor union development and the advancement of workers' rights. Therefore, the correct option is A True.
Step-by-step explanation:
Labor unions formed as a result of various efforts, including those during the Progressive Era, to advocate for workers' rights. This statement is True. Workers' organizations developed in response to poor working conditions and the need for collective representation, which evolved into labor unions that focused on a range of concerns including wages, work hours, safe working conditions, and benefits.
The Progressive Era and subsequent governmental policies, like those under Franklin Roosevelt's administration, played significant roles in the advancement of labor unions and workers' rights. Union membership and influence experienced substantial growth during the 1930s, following the passage of the National Labor Relations Act of 1935 which legalized the labor movement and bolstered union rights.