Final answer:
The Civil War encouraged the growth of unions as it refined and standardized mass production of manufacturing techniques.
Step-by-step explanation:
The Civil War encouraged the growth of unions as it refined and standardized mass production of manufacturing techniques. The industrialized northern states benefited from new technologies and had the capacity to produce more war materials and transport troops to the front more quickly than the South. This led to the growth of unions as they advocated for workers' rights and better working conditions in the booming manufacturing industry.