^Northbound trailblazer leading away from Illinois 15 in Fayetteville, April 2020.
Illinois Route 4 runs mostly north-south in central and southwestern Illinois. Its northern end is in Springfield, and it heads south along a former alignment of US Route 66 until northeast of St. Louis; then it heads south through some far exurban outskirts of the Metro-East before curving southeasterly to end north of Murphysboro. It connects a long list of decently-sized small towns together.
Illinois 4's intersections will be listed from southeast to northwest, since that's the orientation I was facing as I drove it. Side note: how fitting that I drove Illinois Route numbered "4" in the month numbered "4". You can tell I did my clinch of this route in April by the flowering trees like those in the cover photo above!