Final answer:
The Civil War's moniker as the "Second American Revolution" comes from its sweeping social, political, and economic impacts on the United States, like the end of slavery and shifts in federal and state power dynamics.
Step-by-step explanation:
The Civil War has often been called the "Second American Revolution" primarily because of choice C) It led to profound social and political changes, including the end of slavery. Unlike a simple military conflict, the Civil War brought about a transformation of American society at multiple levels. Politically, it signaled the transition to a federal government that held more power over the states.
Economically, it disrupted the South’s agrarian economy while bolstering the North’s industrial base. Socially, it not only ended the institution of slavery but also highlighted class tensions, leading to events such as draft and bread riots.
Historian James McPherson has noted that soldiers fought for cause and comrades, aiming to uphold American values of liberty and freedom in a democratic nation. The war divided communities and even though the Union was ultimately restored, the American way of life had irrevocably changed after the conflict. This comprehensive transformation justifies the Civil War's characterization as a second revolution, reshaping the nation’s identity and values.