Labor unions began to pose a threat to big businesses as far back as 1869. The Knights of Labor was the first 'big union'. Its membership was not restricted by skill or craft. With the rise of the American Federation followed by the Congress of Industrial Organizations and F.D.R.'s New Deal for Labor, several major reforms were legislated into law in order to achieve a balance of power between labor and management.
1. The Wagner Act 1935- gave unions the right of collective bargaining, and defined unfair labor practices. under this legislation Congress created the National Labor Relations Board to act as a 'watchdog' regarding labor-management relations.
2. The Fair Labor Standars Act 1938- created a national minimum wage and guaranteed overtime for workers who worked more than 40 hours a week.
3. Several 'child labor protection' laws helped to stop the exploitation of children, as well as help to establish a push towards mandatory education laws for children in the major urban areas at the beginning of the 20th century.
The basic aims of unions today are largely rooted in the protection of wages,job security, health benefits, and retirement packages. Although labor unions in the United States are not void of corruption and abuses, the favorable Congressional legislation towards union organization during the 1930's helped to establish a 'relationship' between the two opposing forces.
I think the answer depends on the time period of American History. Labor organizations became prominent and permanent staples of the American socio- political landscape in the late 1800s and in the opening of the 20th century. The issues that organized labor staked its reputation concerned worker's rights in the newly industrialized nation. Working conditions in factories, just compensation, hours of work, were but a few of the items that labor unions sought to remedy through social awareness and national legislation. These issues were brought the forefront at that particular period and became a familiar refrain throughout the 20th century work of labor organizations and worker's unions. Legislation that ensured safe work conditions for workers, minimum wage requirements for workers, a fixed work week with overtime wage compensation were but a few of the legislation passed in the second half of the twentieth century, owing much to the Progressive movement of labor unions in the first half of the century.