My teen/ young adult years were spent in a southwest suburb of Chicago, and we commuted downtown on the Rock Island's "Suburban Branch", that left the Chicago/ Joliet Mainline at Gresham, and rolled downgrade from there to run through Beverly Hills and Morgan Park to its terminus at Blue Island.
During those years, most of the commuting stock was the 1920's heavyweight "Al Capone cars" (some of which are preserved at IRM), and later, smooth-sided bi-levels painted yellow over red. The power was a collection of E- or F-units of various vintages, as well as one-offs like the Alco DL-109 "Christine" and the B-unit-like AB6s. I also used to see the AeroTrain fairly often, but never road it, as it was confined to the Main Line, which ran out to Joliet and beyond. (My Dad had taken me downtown to see and walk through the new Aerotrain when it was displayed before its introduction in 1956 , so at least I got to walk the interior.) In the late 70's, my sister commuted on something called "The Dinky", which was supposedly a European version of a doodlebug, but I never rode or even saw it. (Today, that term is reserved for bi-level METRA commuter trains generally.)
My only souvenir of that time was the plastic sleeve that held our monthly tickets, duly printed with" Rock Island Lines" in red ink. The only Rock Island O Gauge items I have are the "bankruptcy blue" GP20 that LCCA put out in 1980, and the similarly-liveried N5c caboose (which , of course, never existed, but I like N5c's generally.)
My great regret was that I wasn't into photography back then, and that I didn't record all that history. "The Rock Island Line was a mighty fine road."