It runs from the Chester Bridge, a truss bridge over the Mississippi River to Route 51 in the state of Missouri, to IL 154 in rural Perry County well west of Pinckneyville.

[1] Illinois 150 generally runs southwest to northeast, but is marked as an east–west route.

A longer concurrency takes place further northeast at Illinois Route 4.

SBI Route 150 originally ran from the US 51/60/62 bridges south of Cairo north to Hamel (located northeast of Saint Louis, Missouri) on what is now Illinois Route 3, the portion of Illinois 150 from Chester to Steeleville, and Illinois Route 4.

[3] Media related to Illinois Route 150 at Wikimedia Commons