Final answer:
The proslavery rebel states took on the name 'Confederate States of America' when they broke away from the United States during the American Civil War.
Step-by-step explanation:
The proslavery rebel states took on the name 'Confederate States of America' when they broke away from the United States. This happened during the American Civil War, which took place from 1861 to 1865. The Confederate states consisted of 11 southern states that seceded from the Union due to disagreements over slavery and states' rights.
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