Illinois Route 78 is a long north-south route in northwestern and west-central Illinois. It's a continuation of Wisconsin Highway 78, running southward from the Wisconsin border all the way to Jacksonville along the Interstate 72 corridor, connecting a great variety of different towns.
Illinois 78 starts as the continuation of Wisconsin Highway 78 crossing the Wisconsin border, entering Warren, Illinois...
Heading south, Illinois 78 joins US Route 20 west into Stockton, Illinois:
In Stockton, Illinois 78 splits off of US Route 20 to resume its southerly pathing:
After passing through Elmwood, Illinois 78 turns southerly again at a wye, leaving Illinois 8 to run independently westward:
Illinois 78 meets Illinois 116 and joins that route west into Farmington:
In Farmington, Illinois 78 splits from Illinois 116 to head southerly again:
Illinois 9 comes from the west, and, at a junction in Canton, it joins Illinois 78 south: (the signage here fails to mention Illinois 9 east)
Leaving Canton, Illinois 9 splits from Illinois 78 to continue easterly:
South of Canton, Illinois 78 meets the northern end of Illinois 100:
In the unincorporated place known as "Little America, Illinois," Illinois 78 joins US Route 24 west:
A few miles to the west, lies a T-intersection where each approach carries a distinct duplex! Illinois 78 splits from US Route 24 to head south, but the western leg of the intersection carrying US Route 24 also carries Illinois 97, which turns onto the southern leg: