16TH ST was located at the crossing of the Chicago and Alton route to Saint Louis and the southwest, the Saint Charles Air Line (jointly owned by the Illinois Central and Chicago, Burlington and Quincy) which provided cross-town freight service with the parallel north south Chicago, Rock Island and Pacific and New York Central (Lakeshore and Michigan Southern) main lines into the iconic LaSalle Street Station. Less than a mile to the west was 21ST ST owned and operated by NYC arch enemy Pennsylvania Railroad with smart brick structure with a Union Switch and Signal interlocked pneumatic plant. If back in the day one had asked which tower would still be up and functioning in 2011 one would have surely assumed the PRR plant, as it was nearly 40 years 16th St's junior and made of more durable materials. However not only was 21St ST closed in 2005, it was completely demolished(!) a few years later leaving 16TH ST to soldier on alone.
Today 16TH ST junction is much reduced from its heyday, but it is still complicated enough to protect the tower from any sort of hasty re-signaling scheme. The Chicago commuter rail authority, Metra, owns and operates the tower as part of its Rock Island division. The parallel NYC main was removed in the early 1970s when Amtrak shifted all passenger operations to Union Station. The former Alton route was merged into the GM&O before that merged with the Illinios Central and was eventually absorbed into Canadian National. The Saint Charles Air Line is now owned jointly by UP, BNSF and CNIC and used for various through-routings as well as Amtrak trains accessing the former IC Main Line to downstate Illinois and eventually New Orleans. A diagram of 16TH ST as it appeared in 1931 can be see at the following link.
16TH ST interlocking is not trivially accessible as it is in the middle of a large brownfield area next to the Chicago river, fenced off from the public. The best way to photograph it outside of riding the Railfan Window equipped METRA Gallery Cars is from the adjacent Orange Line that runs between Midway airport and The Loop. Even then you're going to need a good zoom.
Before we begin I would like to mention that the large format photos are not mine and were provided by one of my sources for this and other explanatory essays. Also the full set of non-captioned photos can be viewed here.
Here we see 16Th St from the southeast showing off the plain black on white lettered nameplate and the operator's parking lot. In the background we can see Roosevelt Ave which provides a popular photo location at the mouth of Chicago Union Station across the river.
As the Orange Line crosses the Rock Island division tracks we see the 68/69 trailing crossover and the 56 switch which forms a wye connection to the Air Line. That connection contains one of the interlocking's more unique features in the form of a diamond crossing over track 2 due to the originally constrained space creating too tight an angle for the track to connect in the usual fashion.
Here we see the tower end on with the CTA Red Line emerging from the downtown tunnel just past the former Alton tracks.
Finally we have a nice high res closeup of the east side of the tower and yeah...its a handyman's dream. Compared with the 1958 pics on Signalbox.org you can see that the siding dates from at least that time. The tower has developed a bit of a sag and half the windows are boarded up internally. Just about the only thing that isn't patched and falling apart is the roof, which was clearly replaced recently. The ladder is some sort of fire code thing, although I don't see how anyone could ever access it. I would not expect this tower to be preserved or to live on much past its eventual closure. It is too small to make a useful C&S/MoW base and its structural integrity probably leaves much to be desired. Also in urban environments towers like these tend to catch fire after being closed although this one standard a good chance of going up even before then.
Here is a diagram of how the interlocking appeared in 1931 with the combined New York Central/Rock Island 4-track trunk line crossing the St. Charles Air Line and Illinois Central lines with assorted connecting tracks. The GRS model 2 machine was far less advanced than the US&S equivalents, which relied more on electric logic. As such points are not worked in pairs so a crossover requires two lever slots (although one lever is a phantom internally slaved to the first). Furthermore signal head gets its own lever and combined with traffic levers for the diamond crossings and lock levers for who knows what one can see why the machine has over 150 total levers.
The diagram is fairly self-explanatory, but in case you are having trouble to the left and right we have the Metra Rock Island tracks. To the north are the two tracks of the CNIC Chicago Sub. To the bottom right we have the CNIC Freeport Sub and to the bottom left we have the Air Line.
Part of the interlocking was re-signaled probably in the 1980s creating a logically separate "North End" where the two main tracks split into 3 for the final mile into LaSalle St Station. The North End represents where the majority of routing decisions have to be made for METRA trains, although the 68/69 switch is used to get trains between track 1 north and track 2 south. The panel is a fairly basic NX push button unit with a fairly minimal display. Like police radios the panel has attracted a number of Banana stickers and, hopefully, a Kitchen Aid logo. The panel makes use of US&S style signaling numbering with L and R suffixes.
According to the Signalbox.org profile 16TH ST was built in 1901 with a 152 lever General Railway Signal Model 2 "pistol grip" interlocking machine. This was a very early example of this machine and used a beefed up version of the Taylor machine grip handle instead of the more iconic "pistol grip" that later became standard. This hybrid machine is the missing link that shows the direct lineage between the Taylor Model 2 (as seen in Willows Tower) and GRS Model 2. If this machine was actually built in 1901 that would indicate some overlap between the Taylor and GRS production runs and as you can see in the 1931 diagram even that is labeled Taylor so exactly how this machine was being branded and sold at the time is a bit uncertain.
Turning right from the model board to look along the GRS Model 2 power frame we can see that this tower is really a dump inside and the plastic sheeting over the windows is an indication of the heroic attempts by operators to keep Chicago's famous wind at bay.
Scooching down a bit to about lever 64 we can get a sense of the number of spare spaces that have developed on the main frame as the plant was rationalized over the tower's 11 decades of service. In the far right corner we can see the 48 lever GRS Model 5 machine that was installed sometime in the 20's or 30s to control a seperate logical section that contained some combination of crossovers with the New York Central, south of the main plant. While these have been completely removed, the old model board and interlocking machine have been remarkably preserved.
Also of interest in this photo are the 68 and 69 levers for the last remaining crossover in the interlocking plant. Because the high voltage current that ran the point machines were routed through contacts on the levers, the pistol grip style machine was limited to powering one set of points per lever due to the electric current limitations of these contacts. Crossovers thus had to use two lever spaces, but were worked in tandem from a single pistol grip with the second lever being omitted. These phantom levers for crossovers are marked with a (#) on the diagram.
Looking back in the opposite direction toward lever 1 from lever 145 we can see the placement of the model board, microwave over and other assorted debris.
Same view with a flash illuminating the high number levers.
Close up side view of the levers starting at about 88 and looking toward 155. Of interest are points lever 92, painted black and traffic lever 94, painted green.
Closeup view of levers 53 through 60. Signal levers 55 and 58 protect the 56 switch, which is part of that crazy diamond turnout I mentioned earlier. The illuminated "56" lamp indicated that those points are locked out due to a cleared route. This was a GRS innovation not found on taylor type machines and would become a hallmark of later Model 2 incarnations.
Another closeup this time of levers 71 through 80. The 76 signal has been displayed for a movement on #1 track northbound and if you go back to the model board you can see the approach light is on for that track. Adjacent to 76 are the 71 and 73 traffic levers that serve...some function, possibly slotting into the CTC territory to the south.
A more extreme side-on view showing the two locked out levers for the routed movement.
Moving to the machine to levers 90 through 122 we can see how the bronze pistol grip handles have all been removed from the spare levers. I guess they break easily so they were needed for spare parts. These levers are responsible for the CNIC routings from the Chicago to Freeport Subs.
Closeup of levers 106 through 113 showing the the home made Normal/Reverse point indicator on 107 that has been applied to all of the switch levers.
Close side view of the pistol grips for those same levers.
Opposite close side view looking down from about lever 128. The 120 traffic lever is reverse and if you look closely you can see it does not have a grip safety as the others do. This is because the grip device actually engages the interlocking mechanics and will only release if the mechanical interlocking allows it. The traffic levers were installed with the advent of CTC and the general re-signaling of the surrounding rail lines. As these levers only use electric locking they were not provided with a grip release.
Looking down the top of the ancient power frame past the illuminated model board we can see the glass globe timers and the power board with its fuses and Voltage/Amp meters for the electric point machines.
Hiding behind a bunch of schedules and timetables is an original interlocking diagram that was glass framed and posed in the tower for somebody's reference. You can get some idea of how complex this whole plant used to be in its heyday. Also above the diagram is an clever little diagrammed flow chart showing the manipulation sequences for the various routes and other information useful in routing trains.
No tower visit would be complete without a trip to the relay room!! Lots of glass cased relays literally hanging off of wooden planks. Can you say fire hazard? I don't know why they call modern stuff "solid state". These old school relays are about as solid as it gets!!
Another fine view of cutting edge turn of the century electronics. Err, that would be turn of LAST century. Hmmm, I wonder if any of these are original? Ugh, I would hate to be the guy who's job it is to debug this mess. Look at that rats nest of wires behind the boards!!
Below the relays we have a bunch of termination blocks, some odd looking devices with induction coils and an advanced 19th century flameless light source
Not sure what these comparatively futuristic looking racks are, but they probably have something to do with the Panel-ized North End.
Looking west from the tower we see the twin Strauss type bascule drawbridges over the Chicago River. The bridge on the left is in use by the Saint Charles Air Line. The bridge on the right is the old B&O Chicago Terminal bridge to the long since demolished Grand Central Station. The B&O had to enter Chicago via a round about route to the south passing through Dolton Junction before turning north through Brighton Park and eventually heading back east along the CB&Q main before crossing the Chicago river and making a hard turn to the North again to finally reach its station. No wonder the B&O chose to market its trains on luxury and not speed.
Anyway, the drawbridges were both controlled by a B&O operator sitting in a tower/bridge cabin between them. Even as the B&Os passenger service ended the railroad and its successor organization, CSX, were still responsible for the interlocking and mantanence of BOTH bridges. To quote Wikipedia, "This has led to a curious historical oddity, as the CSX, successor railroad to the B&O, owns a bridge that it cannot abandon, because the bridge is needed to continue operating a second bridge it does not own."
Looking at the signals we can see a mast and a reverse direction dwarf protecting the drawbridge. The mast only has two lights, but if CB&Q signal rules are in use that would be enough to display Stop (R), Restricting (*R*), Approach (Y) and Approach Medium (*Y*). Talk about efficient use of lamps! On the inbound tracks the reverse direction is protected by what appears to be an old style 2 lamp US&S dwarf and a new two headed modular traffic light mast. On the eastward track however there is the 141/142 signal immediately before the switch to the Rock Island connector and then 250 to the west an outer signal 151 (on an old style mast with pointy finial no less!) What the point of having two signals 250 feet apart is I have no idea, but hey, whatever keeps more levers active.
Looking north from the rear of the tower we catch a Metra commuter train being pushed by F40PH #102 on a diverging movement from track 1 to track 1. You can see how close the panel operated "North End" is and how it is separated from the power frame section by a pair of double headed intermediate controlled signals.
Stepping back outside and across the tracks we see F40PH-2 #180 heading southbound with a newer MP36PH-3S waiting on track 2 behind it. Track #2 has a clear signal northbound probably because the Metra 47th St shoppes/yard are located on the west side of the tracks, so during peak periods it would reduce conflicts to wrong rail layup moves on #2 instead of cross them over.
I will leave you with this photo of MP36PH-3S #408 heading southbound across the diamonds with another train of gallery cars and 16TH ST tower in the background. Towers aren't the only thing Metra takes good care of as some of those gallery cars are over 50 years old!!
Coming up next in this series is Metra's UD tower in Joliet.