Which issue intensified in the debates over westward expansion after the Mexican War?

• A. Tariffs and trade.
• B. Currency reform.
• C. Slavery expansion; conflict between free and slave states.
• D. Immigration policy.

Answer: (C)

The central idea is whether slavery would expand into the new western lands won after the Mexican War. Gaining vast territories from the Mexican Cession meant deciding if these areas would permit slavery, which would shift the political balance between free and slave states in Congress. That potential shift intensified sectional tensions and made debates over how to handle statehood and laws in those territories the dominant national issue. Attempts to resolve it, like the Compromise of 1850 and related debates, only highlighted how central the question of slavery’s spread was to the future of the Union. While tariffs, currency issues, and immigration policy mattered in other contexts, they did not drive the intense, immediate conflict tied to westward expansion and the fate of slavery in new territories.