Final answer:
The Northwest Ordinance set up a system for territories to become states, prohibited slavery in new territories, and assured basic freedoms, playing a key role in the organized expansion of the United States.
Step-by-step explanation:
The Northwest Ordinance influenced the expansion of the United States by establishing a system for the admission of new states into the Union, setting a precedent for organized territorial government and the orderly expansion of the United States. It also barred slavery in the new territories, except as a criminal punishment, and established a Bill of Rights that guaranteed fundamental freedoms such as representative government, religious freedom, and trial by jury. Through the Northwest Ordinance, territories with a sufficient population could draft a constitution that forbade slavery and seek admission to the Union as new states, thereby providing a framework for future expansion that aligned with American ideals of freedom and self-governance.