Final answer:
John L. Lewis was the head of the United Mine Workers, a skilled labor negotiator who played a critical role in the labor movement and the formation of the CIO, often achieving substantial gains for miners.
Step-by-step explanation:
The head of the United Mine Workers was John L. Lewis. He was a prominent labor leader known for his role in elevating the plight of the coal miners through strikes and negotiations for better wages and working conditions. His tenure as leader of the union made him a central figure in the labor movement, particularly through his involvement in creating the Congress of Industrial Organizations (CIO). Lewis was known for his success in negotiating higher wages for miners, but also faced criticism for calling labor strikes during World War II.
Lewis's strategies often put him at odds with the government, especially when he called for strikes during times of national need, such as World War II. Despite the contention, these strikes often resulted in significant gains for the miners, such as wage increases and improved labor rights. His leadership played a crucial role in the labor movement's growth and influence during the mid-20th century.