Illinois Route 105 is a jagged route, though its overall pathing is east-west, connecting Decatur to points east and northeast, eventually ending in Monticello. It's somewhat of a local alternative to Interstate 72 that connects to various communities south of that freeway.
The western end of Illinois 105 is at Illinois 48 on the southwest side of Decatur:
After wrapping around the south side of Decatur, Illinois 105 turns northerly to wrap around the east side of town, where it crosses US Route 36 and picks up Illinois 121 for a short concurrency:
After a block-long concurrency, Illinois 105 splits to head eastward out of Decatur, as Illinois 121 picks up where Illinois 105 left off wrapping around the east side of town:
Having begun to traverse a decidedly more rural landscape, Illinois 105 reaches Illinois 32, which it joins northerly into Cerro Gordo:
Then, when in Cerro Gordo, Illinois 105 cuts away from Illinois 32 to resume going easterly:
The easterly direction of Illinois 105 ends just south of Bement, and Illinois 105 turns northerly through Bement and beyond:
After serving as the main thoroughfare through Monticello, Illinois 105 ends at a folded diamond interchange with Interstate 72. As Illinois 105 is heading northerly in this section, the endpoint feels more like a northern endpoint than an eastern endpoint: