Final answer:
The Knights of Labor grew due to their inclusive membership policies and advocacy for social reforms but declined due to association with violence, internal disputes, and competition from other labor organizations.
Step-by-step explanation:
The Knights of Labor grew so large primarily due to their inclusive membership policies, which attracted a diverse group of laborers, including women and African Americans, during a time when such inclusivity was unique to labor unions.
They aimed for broad social reforms, such as the elimination of child labor, establishing minimum wages and maximum hours, and even the collective ownership of factories, appealing to workers who sought a more equitable distribution of profits and control over their workplaces.
However, their membership declined due to reasons such as being mistakenly associated with violence following the Haymarket Square incident, internal disputes between skilled and unskilled workers, and competition from other labor organizations like the American Federation of Labor (AFL).