This module explains the origins and development of the American Federation of Labor and Congress of Industrial Organizations, the largest federation of unions in the United States. Apprentices learn how the AFL-CIO brought together diverse trades to strengthen the labor movement, advocate for workers’ rights, and influence national labor policies. The unit also emphasizes the connection between union solidarity and the improved wages, benefits, and protections that workers enjoy today. By studying this history, apprentices gain a deeper appreciation of the role organized labor continues to play in shaping fair and safe workplaces.