Final answer:
The significant legislations are the National Labor Relations Act (1935), the Taft-Hartley Act (1947), and the Fair Labor Standards Act (1938), which collectively established workers' rights to unionize and set standards for wages, hours, and working conditions.
Step-by-step explanation:
The three pieces of legislation that have been most important in defining the rights of management and unions are the National Labor Relations Act of 1935 (also known as the Wagner Act), the Taft-Hartley Act of 1947, and the Fair Labor Standards Act of 1938. The Wagner Act was pivotal because it granted workers the right to organize unions and required management to give them a fair chance to do so. The Taft-Hartley Act altered the legal environment, giving states the authority to allow workers to refrain from joining unions, thereby marking the start of a decline in union membership. Finally, the Fair Labor Standards Act established minimum wage, maximum hours, and other employment standards to protect workers' interests.
These laws collectively have helped establish a balance of power between employers and workers, by setting employment standards, regulating health and safety, and preventing workplace discrimination. However, the passage of the Taft-Hartley Act, in particular, indicated a shift to a less union-friendly legal climate which contributed to a decline in union memberships over time.