Illinois Route 84 is the westernmost north-south highway in northwestern Illinois, connecting Galena to the Quad Cities, occasionally within sight of the Mississippi River. The Great River Road follows Illinois 84 upstream of the Quad Cities.
Illinois Route 84's northern end is at the Wisconsin border north of Galena, where it becomes Wisconsin Highway 80...
On the west side of Galena, Illinois 84 joins US Route 20 eastward through that town...
East of Galena, Illinois 84 splits from US Route 20 to resume going southward....
In Savanna, US Route 52 and Illinois 64 come from a bridge over the Mississippi River, to join Illinois 84...
Illinois 84 soon splits from US Route 52 and Illinois 64, who become longtime friends heading east, and Illinois 84 continues southward...
Illinois 84 crosses Illinois 136 at Fulton, Illinois, the town across the river from Clinton, Iowa:
Illinois 84 crosses US Route 30 across the river from Clinton, Iowa...
Illinois 84 joins Illinois 92 eastward through Silvis, a town on the east side of the Quad Cities metropolitan area...
Illinois 84 crosses under Illinois 5 with an interchange providing access, and Illinois 92 joins that route eastward, leaving Illinois 84 to continue southeast independently...
Illinois 84 meets its southern end by Colona; this is just northwest of the junction of Interstates80, 74, and 280: