Final answer:
The Northwest Ordinance of 1787 prohibited slavery in the new territories, established a process for becoming states, and laid out a grid system for land sales.
Step-by-step explanation:
The Northwest Ordinance of 1787 had multiple significant impacts on the territories north of the Ohio River. Most prominently, it prohibited slavery in the new territories, with the exception of punishing crimes and requiring the return of fugitive slaves. It created an orderly process for the territories to become states, starting with rule by a governor and judges appointed by Congress and progressing to a popularly elected legislature and eventual statehood once certain population milestones were reached. The Ordinance also provided for the establishment of a grid system for land sales and reserved land for civic purposes, like schools, illustrating the nation's plans for an organized expansion westward.