The highway heads north passing a large, coal fired power plant (Rockport Generating Station) and through farmland towards Chrisney; the expressway then intersects with SR 70.

The route turns northeast, passing through woods, just south of Lincoln State Park.

From this point northward through the remainder of Southern Indiana, the highway will remain mostly a rural two-lane road.

North of downtown Huntingburg, the road passes through commercial properties, before leaving town.

The concurrency travels due north, then turns northeast and enters downtown Loogootee.

The highway then heads north towards Bloomfield, passing the Naval Surface Warfare Center Crane Division.

The highway enters Greencastle from the southeast and begins to turn north, passing DePauw University to the west.

On the south side of Crawfordsville, the route becomes a four-lane undivided highway, passing through commercial development.

Through the north side of Crawfordsville, the road passes through mainly residential land, with a few commercial properties near the interchange with I–74.

On the way to Lafayette, the route passes through rural farmland, paralleling a CSX rail line.

[7] The road enters Lafayette and becomes a four-lane divided highway as it runs through a mix of farmland and residential areas.

It passes a few commercial properties, and then a few miles west, US 231 leaves the concurrency, while US 52 continues northwest and US 231 heads due north.

After Wolcott, the concurrency crosses into Jasper County and into the Central Time Zone.

The road then enters Rensselaer, heads north and turns northeast, with a traffic light at SR 114.

North of the traffic light, the road makes a sharp turn and heads northwest.

After 2.5 miles (4.0 km), the concurrency ends, with SR 10 traveling south and US 231 continuing north.

[5][6] North of the Kankakee River, the route begins a concurrency with SR 2 at a four-way stop south of Hebron.

The road leaves Hebron, passing more residential properties and heading towards Crown Point.

The road then begins a concurrency with SR 55 and the two highways head for downtown Crown Point.

In downtown Crown Point, the routes go around the county courthouse on one-way streets.

US 231 then leaves Crown Point, heading towards its northern terminus on the south side of St. John.

[5][21] In Northern Indiana, a new routing of US 231 around the south and west sides of the Lafayette/West Lafayette area opened September 13, 2013.

[8] Previously, US 231 entered downtown Lafayette from the south on 4th Street, passed over the Wabash River on the Harrison Bridge, then continued north and northwest in West Lafayette on Northwestern Avenue passing Purdue University, until merging with US 52.

A project is planned that will possibly put US 231 on a four-lane divided highway around Huntingburg and Jasper in the southern part of the state.

[27] Indiana has invested in a strip of "electrified highway that could charge even the largest vehicles as they drive over it" on US 231.

[28] Research on the project is being conducted by Purdue University's Steve Pekarek, who says the technology could make a transition to electric vehicles more attractive.