Which national labor union was the first to be founded in the U.S.?

The Knights of Labor was the first significant national labor union established in the United States, formed in 1869. This organization sought to unite all workers, regardless of skill level, race, or gender, and aimed to improve their working conditions, wages, and hours. The Knights of Labor played a vital role in advocating for worker rights and emphasizing the importance of solidarity among the working class.

In contrast, the American Federation of Labor, established in 1886, primarily focused on skilled workers and aimed to organize labor unions to protect their specific interests. The Congress of Industrial Organizations (CIO) was created in the 1930s and sought to represent industrial workers. The Union of Industrial Workers is not a historically recognized organization in the same context as the others mentioned.

The Knights of Labor's pioneering efforts laid the groundwork for the labor movement in America, marking it as a significant milestone in the history of labor organizing.