Final answer:
The most popular labor union during the Gilded Age was the American Federation of Labor (AFL), founded by Samuel Gompers. The AFL focused on representing skilled craft workers and fought for higher wages and shorter work weeks.
Step-by-step explanation:
The most popular labor union during the Gilded Age was the American Federation of Labor (AFL). Founded by Samuel Gompers, the AFL focused on representing skilled craft workers and fought for higher wages and shorter work weeks. By 1914, the AFL had more than 2 million members and played a significant role in improving working conditions for its members.