Final answer:
According to the Northwest Ordinance of 1787, a territory could write a constitution and apply to become a state when the population exceeded 60,000 inhabitants.
Step-by-step explanation:
The Northwest Ordinance of 1787 outlined the process by which territories could become states within the United States. According to the ordinance, once a territory's population exceeded 60,000 inhabitants, it could draft a constitution that upheld certain principles, such as forbidding slavery and ensuring religious freedom, and then apply for statehood. This measure was one of the significant achievements of the Confederation Congress, providing an orderly system for the expansion of the nation and managing the settlement of western territories, with self-government being a precursor to achieving statehood.