The Congress of Industrial Organizations (CIO) was a major labor organization in the United States, founded in 1935. It aimed to organize workers in mass production industries, such as steel and automobiles, to improve their working conditions and wages. The CIO played a crucial role in the labor movement during the Great Depression, advocating for workers' rights and collective bargaining. In 1955, the CIO merged with the American Federation of Labor (AFL) to form the AFL-CIO, creating a more unified labor movement. The CIO's legacy includes significant advancements in labor rights and the establishment of unions that continue to represent workers today.