Answer:
A key issue was states' rights and territorial expansion.
Step-by-step explanation:
states rights:
The Southern states wanted to assert their authority over the federal government so they could abolish federal laws they didn't support, especially laws interfering with the South's right to keep slaves and take them wherever they wished.
territorial expansion:
The South wished to take slavery into the western territories, while the North was committed to keeping them open to white labor alone.