Much like the First Subdivision, the Second Sub was built early in Illinois' railroading history, having been completed as the Peoria and Bureau Valley from a connection with the C&RI at Bureau to Peoria by 9-Nov-1954. The P&BV never really operated their own line - the company constructed it and then immediately leased it back to the Chicago & Rock Island for operation. Over time, it was formally folded into the Rock Island system around 1950. CSXT acquired the line from Bureau to Henry in order to continue service to the Goodrich chemical plant just north of Henry. The rest of the line to Peoria was saved by the Lincoln & Southern Railroad, owned by BF Goodrich, presumably to provide competitive pressure to keep CSX's prices in line. In 1987, the L&S granted Iowa Interstate operating rights over everything between Henry and Peoria. In early 2006, IAIS signed a lease on the northern half of the line from CSXT, taking over operations on 4-Feb-2006.

Today, the Second Sub gives IAIS a direct connection into Peoria, which provides it with incoming loaded coal trains bound for Cedar Rapids, as well as a more southern outlet for grain during the winter when the Upper Mississippi freezes. The line is primarily served by irregular extras (the unit coal and grain drags), as well as the Peoria local (otherwise known as the Bureau Rocket, a roadswitching job based out of Bureau). The local goes on duty at 1000h on weekdays, and works the line as needed. The coal drags run about once a week (loads up, empties back a couple days later), and the grain trains run as needed, primarily during the winter months.

IOWA INTERSTATE RAILROAD - SECOND SUBDIVISION BUREAU, IL, TO PEORIA, IL Maximum Speed: 25 MPH on IAIS track Length: 43.3 miles Entire line Track Warrant Control Radio: IAIS - 161.220 MHz and 160.305 MHz from MP127.7 to MP 157.5 CSXT - 160.320 MHz and 160.290 MHz from MP 114.2 to MP 127.7 PPU - 160.470 MHz in the Peoria area
	Mile Post	Station	Sidings	Other Tracks		Notes
W E S T B O U N D	114.2	Bureau, IL	5290	Yes	E A S T B O U N D	Junction with Subdivision 1
	122.1	Putnam
	126.5	Goodrich
	127.7	Henry	3614	Yes
	134.7	Sparland		Yes
	142.6	Chillicothe	665			BNSF Interchange
	144.1	Coughlin
	151.1	Mossville		Yes
	157.5	Peoria, IL		Yes		PPU Interchange

Timetable Legend: