Labor unions are organized associations of workers formed to protect and advance their rights and interests, particularly in negotiations with employers regarding wages, working conditions, and benefits. They play a critical role in advocating for workers during periods of economic and social transformation, such as those seen in the post-Civil War era and the rapid industrialization of the United States. Labor unions emerged as a response to the harsh realities of working conditions and the rise of big businesses that often prioritized profit over employee welfare.