Which article of the constitution made all state laws equal to each other?

 Article 4 – States Rights.

Section 1 A. All states will honor the laws of all other states. Section 2 A. Citizens of one state are treated equally and fairly like all citizens of another.

Explanation:

New territories and states were formed as the US expanded westward, creating conflict over the legality of slavery in the new states AND the role of national government over state’s rights. The civil war was eventually born out of southern frustrations with northern authority (including commerce control and slavery), only exasperated by westward expansionism.