Its northern terminus is at U.S. Route 169 in northwestern De Kalb County; its southern terminus is at US 169 southeast of St. Joseph.

Its northern terminus was originally five miles further north in King City at Route 4.

Route 31 runs east, concurrent with 36, where it moves into DeKalb County, before they split at the intersection with Spruce Road.

The routes run through Clarksdale after the merge, before they turn east and split.

Route 31 runs north, before once again meeting with US 169 at the former's northern terminus.