The former Rock Island main line from Blue Island (Chicago) to Council Bluffs is now operated, and mostly owned, by the Iowa Interstate railroad. Once double track, current-of-traffic, Automatic Block Signals, the line is now single track, Track Warrant Control, unsignaled (dark territory), maximum speed 49 mph. From the wye at Yocum Connection (MP 259.0), where it connects with the CRANDIC Third sub., the IAIS heads east-southeast, past a dirt track grade crossing, the east apex of the wye at Homestead (MP 256.6), a grade crossing and extra track to the north, turning south-southeast, past a grade crossing, two dirt road grade crossings, silos to the south (no rail) at Oxford (MP 251.5), a grade crossing, and a street alongside to the north, and then east, and southeast, east a detector at MP 248.2, a bridge over a stream, a dirt road grade crossing, a grade crossing, streets both north and south in Tiffin (MP 244.6), two grade crossings, a rail-served plant to the south, a grade crossing, extra track to silos to the north, and a grade crossing.
The line turns southeast, past dual angled road bridges overhead (I-80), a grade crossing, a dirt track grade crossing, a road alongside to the north, a divided highway grade crossing, Hawkeye (MP 242.7), a grade crossing, a driveway grade crossing, a bridge over a stream, Vernon (MP 241.0), a bridge over a footpath, a bridge over a divded highway, a grade crossing, a road bridge overhead, Stadium (MP 238.0), a grade crossing, east, past the nine span Iowa River Bridge (MP 237.1), which also bridges over a street to the west of the river and the south end of the CRANDIC First sub., and another street, east of the river, a grade crossing, the four track yard (closed October 29, 2012, in favor of South Amana) to the south and siding to the north at Iowa City (MP 236.8), where the depot is to the north, a bridge over a stream, a bridge over a street, two road bridges overhead, a single track to the south, a grade crossing at First Avenue, two spurs curving away to the south, rail-served silos to the south, a grade crossing, and a rail-served plant to the south.
There is a grade crossing, a turn east-southeast, an angled grade crossing, a road bridge overhead, a turn east, Midway (MP 231.1), two dirt road grade crossings, a grade crossing, Downey (MP 226.3), a spindly road bridge overhead, a detector at MP 224.8, a turn southeast, a west-facing spur to industry on the south side, a grade crossing, the 4,200 ft siding at West Liberty (MP 221.3), where erstwhile Rock Island lines once headed both north and south, with the depot on the north side and an old wooden caboose north of the depot, three grade crossings, a turn east, an angled grade crossing, Atalissa (MP 215.9), a turn northast, three grade crossings, a turn east-southeast, a dirt road grade crossing, a grade crossing, the ten-span deck girder Cedar River Bridge (MP 211.8), a dirt road grade crossing, a grade crossing, a rail-served scrapyard to the north, Moscow (MP 211.5), and a spur heading away north.
The line turns east-northeast, past the siding at North Star (MP 210.0), two grade crossings, Wilton (MP 207.6), with brick depot to the south, two grade crossings, a dirt track driveway crossing, the 5,360 ft. north-side siding at Twin States (MP 203.2), and a road alongside to the north, east-southeast, past a driveway grade crossing and a spur trailing in on the south side, both for an industry, Durant (MP 202.0), a spur curving away south at Stockton (MP 199.2), where erstwhile Rock Island lines once headed northwest and southeast, six grade crossings, the siding at Walcott (MP 194.2), a dirt road grade crossing, and a grade crossing, curvily southeast past the bridge over I-280 (MP 189.8), an angled grade crossing, Brammer (MP 186.3), two grade crossings, a bridge over a stream, and a spur to silos to the south at Farname (MP 186.2), south, past a grade crossing, and east, past a road bridge overhead, to Missouri Division Junction (MP 183.7), where the remnants of the Golden State Route line trail in on the south side.