Answer:
The tendency of northerners and southerners to settle, respectively, in northern and southern sections of the Old Northwest.
Step-by-step explanation:
The "Old Northwest" was the name that was given to the Northwest Territory in the United States. This was a territory formed after the American Revolutionary War. This encompassed the land west of the Appalachian mountains, north of the Ohio River. Although both Northerners and Southerners used to settle on this land, Northerners settled in the northern sections, while Southerners settled in the southern ones.