The document discusses several key changes in the late 19th century that led to the rise of organized labor movements in the United States, including the replacement of skilled jobs by machines, declining wages and working conditions, and the prevalence of child labor. It notes over 2 million children under age 15 worked long hours in unsafe conditions. This poor treatment of workers led unions to form to advocate for better pay, hours, and workplace safety. However, organized labor faced opposition from business owners and difficulties coordinating strikes. The document also summarizes women joining the workforce and progressive era reforms targeting political corruption and unsanitary conditions exposed by muckrakers like Upton Sinclair.