How did the northwest ordinance set the tone for the future development of the united states

For one, the territory system installed by the Northwest Ordinance would remain the standard for admittance to Union throughout the continental United States throughout the era of expansion; also, the system of popular sovereignty over slavery would become commonplace, up until its influence played a role in the start of the Civil War in the 1860's.

To be honest i thinks its between the first answer and the third answer