Metra Electric does indeed have a unique and interesting history. It's hard to imagine that this route was actually a steam road in the beginning, before electrification was completed in 1926. Very few, if any, tangible remnants from that era exist today, with the possible exception of the commuter platforms currently in use at Roosevelt Road. Although used only by Metra and NICTD trains today, these platforms were at one time within the domain of Central Station, originally built in 1856, which was once the home of Illinois Central's long distance passenger trains between Chicago and the south. More info can be found here:
www.encyclopedia.chicagohistory.org/pages/627.html
During the decades following the Great Depression of 1929, many blacks migrated here from the south looking for a better life and more oppurtunities, and those who bought a one-way ticket to Chicago coming from Mississippi, Alabama, or Georgia normally wound up on trains such as The City of Miami, The Seminole Limited, (between Chicago and Jacksonville), and the City of New Orleans. My grandmother was among those migrants, arriving here from Alabama in 1945, and she remembers Central Station as being "the biggest building I'd ever seen in my life". Coming from a small town in the south, I'm sure many other people felt the same way.
With the 5/1/71 formation of Amtrak, I believe some intercity passenger trains still used the station, but all had moved to Union Station by 1972, and the station building was demolished two years later. Meanwhile, the Seminole Limited was trimmed back to Carbondale in 1969, and was renamed the Shawnee, which was transferred to Amtrak by that name two years later. It is now known as the Illini. As for The City of Miami, it was actually a joint operation between IC and Central of Georgia, with the latter road running the train east of Birmingham. Today, Norfolk Southern owns and operates most of the trackage between Birmingham and Jacksonville, although I don't know for sure if passenger service on this segment survived into the Amtrak era, if it did at all.
But getting back to Metra Electric, I believe the South Chicago Branch is the only line on Metra's system where commuter equipment is not stored overnight. After shuttle 353 finishes its final run at 93rd St., it deadheads back to Randolph St. But at one time, rush hour equipment did lay over on nights and weekends on a short spur around 81st St., or so, don't remember the exact location, or when this practice was discontinued.