[2] Owing to its role in the state's history, the county motto is "Where Illinois Began."

George Rogers Clark of the army of Virginia captured the area from the British on July 4, 1778, near the end of the Revolutionary War.

The area then became the seat, for several years, of Illinois County, Virginia, although the Congress of the Confederation legislated the existence of the Northwest Territory on July 13, 1787.

Crains Island,[3] southeast of Chester, is another enclave of Illinois west of the Mississippi that was created by a change in the river's course.

The Mississippi changed its course in the late-nineteenth century, leaving Kaskaskia, the former state capital, on the west side of the river.

As of the 2010 United States census, there were 33,476 people, 12,314 households, and 8,188 families residing in the county.

[18] Randolph is a rural conservative county in southern Illinois that has trended Republican since 2000 in presidential elections.

There are two AM radio stations licensed in the county — WHCO 1230AM in Sparta and KSGM 980AM in Chester.