At its inception the Territory was a vast wilderness sparsely populated by nomadic Indians including the Delaware, Miami, Potawatomi, Shawnee and others; there were only a handful of French colonial settlements, and Clarksville at Falls of the Ohio. At the territory's dissolution, there were dozens of towns and settlements, a few with thousands of settlers, mostly in Ohio chiefly along the Ohio and Miami Rivers and around the Great Lakes.
Initially, the Territory was governed by martial law under a governor and three judges, but as population increased, a legislature, the Territorial General Assembly, was formed. Administratively, the Territory was divided into a succession of counties, eventually totaling 13.
The Northwest Territory included all the then-owned land of the United States west of Pennsylvania, east of the Mississippi River, and northwest of the Ohio River. It incorporated most of the former Ohio Country except a portion in western Pennsylvania, and Illinois Country. It covered all of the modern states of Ohio, Indiana, Illinois, Michigan, and Wisconsin, as well as the northeastern part of Minnesota. Lands west of the Mississippi River were the Louisiana Province of New France (acquired by the United States in 1803 by the Louisiana Purchase); lands north of the Great Lakes were the British Province of Upper Canada, and lands south of the Ohio River constituted Kentucky County, Virginia, admitted to the union as the state of Kentucky in 1792. The area included more than 260,000 square miles (670,000 km2) and comprised about 1/3 of the land area of the United States at the time of its creation. It was inhabited by about 45,000 Native Americans and 4,000 traders, mostly Canadien and British. Among the tribes inhabiting the region were the Shawnee, Delaware, Miami, Wyandot, Ottawa and Potawatomi. Notably, the Miami capital along with British trading posts was at Kekionga at the site of present day Fort Wayne, Indiana. Neutralizing Kekionga became the focus of the Northwest Indian War, the driving events in the early evolution of the territory.
The state cessions that eventually allowed for the creation of the Territories North and South West of the River Ohio