At Bridgeport (MP 3.1), the IC tracks fork, with the former GM&O, former Alton line turning southwest, and the IC line west to Iowa turning due west, with two Santa Fe tracks now alongside it to the south, operated as Four Main Tracks, CTC, with speed limit 30 mph from this point west to Ash Street (MP 4.4), where there is a connector in the southeast quadrant and flat crossings with the Rock Island, the B&OCT, and the PRR Panhandle lines (speed limit 15 mph on the crossings), all coming south across the Chicago River (just north of the flat crossings) on the famous quad bridges.
West of Ash Street, the IC and Santa Fe line continue adjacent, but are operated separately, with the speed limit rising to 79 mph for passenger trains and 55 mph for most freight trains on the Two Main Tracks, CTC, of the Santa Fe, along the south bank of the Chicago River, with the IC line turning away across the river and the Santa Fe line continuing along the south bank past ATSF Crossing, Corwith (MP 5.9), a flat crossing with the ATSF-owned Illinois Northern coming south across the river and headed to Corwith Yard, speed limit 50 mph on the crossing, with the main connector from Corwith Yard curving west to come alongside the main line at Junction Yard on the south side of the main, with the IC Joliet line just to its south.
There is a flat crossing with the Belt Railway of Chicago line coming south across the river at Nerska (Chicago Belt Crossing, MP 7.3), with speed limit 40 mph on the crossing, a curve between MP 9.0 and MP 9.4, with speed limit 60-50, the 3,600 ft. spur on the south side at Waterways Terminal (MP 9.7), a curve to the northwest and the bridge across the CS&S Canal (as the man-made extension of the Chicago River has become) and then a curve back to the west between MP 9.7 and MP 10.3, with speed limit 30 mph, curves to the west-southwest and then the southwest between MP 10.7 and MP 12.2, with speed limit 65-60, the yard on both sides of the line at McCook (MP 12.8), and then the flat crossing with connectors in all four quadrants with the Indiana Harbor Belt, a former B&OCT line, at BOCT Xing (MP 12.9), with speed limit 50 mph on the crossing.