IL-125 follows most of the route of the Sangamon Trail, a pioneer trail from Springfield, the state capital, to the Illinois River. Points of interest directly located on IL-125 include the Clayville Tavern, an 1824 hostelry located 2 miles (3.2 km) east of Pleasant Plains, and the Illinois River bluff at Bluff Springs, five miles (8 km) east of Beardstown and the river.
SBI Route 125 originally ran from Springfield to Virginia. In 1968 it was extended west to Beardstown, replacing U.S. 67 and parts of Illinois Route 3. The next year it was truncated on its eastern portion from Springfield to Illinois 97. There have been no changes to Illinois 125 since 1969.[2]