From the flat crossing with the Alton & Southern, with western and southern quadrant connectors at A&S Junction (MP 6.3), the maximum speed rises to 35 mph as the line heads southeast, single track, Automatic Block Signals, past the yard on the north side at Coapman Yard (MP 8.3), where the maximum speed rises to 50 mph, turning east-southeast to a location where an erstwhile routing continued ahead but today's routing turns sharply southwest, and then makes a big counter-clockwise horseshoe curve to come alongside the north side of the Illinois Central line to Du Quoin, which has also been rerouted to this location,, heading northeast, with both lines turning southeast and then east, where they separate, with the IC turning away south and the NS turning east-northeast, east-southeast past a former bridge carrying the erstwhile Peabody Short Line, and then southeast, onto its original routing, having missed the locations of Lake, Pittsburg, Harmony, Lenz and Gartside on the erstwhile routing.
There is a detector at MP 13.2, Yoch, a spur at Belleville (MP 15.8), formerly Belleville Junction, where a branch to Belleville once left on the south side and the line turns east, east-southeast, northeast where an erstwhile connector to the erstwhile former L&N once left on the north side, North Belleville, a bridge carrying the MetroLink light rail line overhead (on the same routing as the erstwhile former L&N line), a turn east-southeast and then east, Little Oak Mine, Shiloh, a detector at MP 24.9, Scott Air Force Base (MP 25.2), Grassland, the 10,299 ft. north side siding at New Baden (MP 34.5), a turn northeast, a spur at Albers (MP 37.8), a detector at MP 37.9, the junction with the spur on the south side to the Monterey Mine xxx at Monterey Mine (MP 38.6), a turn east to Germantown, a turn southeast, a turn east again, a spur at Bartelso (MP 46.2), Zachery, a detector at MP 48.8, a spur at Posey (MP 52.9), a jog northeast and then east again, a jog further northeast and then east again, a spur at Hoffman (MP 57.6), and a detector at MP 60.9, where there is a further jog northeast and then east again.
Yard Limits and a 20 mph speed restriction start at the 6,980 ft. north side siding at Centralia (MP 64.2), at the east end of which is the junction with the double track, Yard Limits, former CB&Q southern Illinois coal line at BN Junction (MP 64.4/MP 121.0), the south end of the BN Centralia yard, where a 10 mph speed restriction starts, on the BN line used jointly, heading just west of due south, past the start of Two Main Tracks, CTC at MP 121.3, the end of CTC and start of single track, Yard Limits, and the very acute-angled junction with the Illinois Central main line at Long Crossover (MP 121.6), where the IC Centralia depot is on the east side of the tracks, the former junction with the erstwhile Missouri-Illinois (later part of the MoPac), the very acute-angled flat crossing with the IC main line at IC Xing (MP 122.3), after which the joint line is finally on the east side of the IC main line, and the junction where the former Southern leaves the joint trackage with the former CB&Q (heading south-southeast) at Southern (Railway) Junction (MP 122.6/MP 66.2), turning away east-southeast.