7 votes

St. Charles Air Line Bridge


Photo taken by Steve Conro in September 2012


BH Photo #240482


Street Views 


St Charles Air Line Bridge

Ryan Jacobs

Play video on YouTube


The St. Charles Air Line (SCAL) Bridge was the world’s longest and heaviest single-leaf bridge when completed in 1919. Designed by the acclaimed Chicago bridge engineer Joseph B. Strauss, the SCAL Bridge was built using many of the design principles as the Chicago & Northwestern Railway Bridge (constructed in 1908). However, the SCAL Bridge is significant because it is an excellent example of a “heel trunnion” bascule bridge, a design developed by Strauss specifically for long bascule spans.

-Commission on Chicago Landmarks, Historic Chicago Railroad Bridges report

The Southern most bridge in the down position is the SCAL bridge and is still in use by the CNRR. The Northern, stored in the up position is the B&O/Chicago Terminal RR Bridge and is now abandoned.


Railroad Baltimore trough truss bascule bridge over the Chicago River near downtown Chicago
Chicago, Cook County, Illinois
Open to traffic
Future prospects
Facing possible closure/demolition
Built in 1919, original length was 260 ft. -- later shortened to 220 ft. in 1930
- Strauss Bascule Bridge Co. of Chicago, Illinois
- Amtrak (AMTK)
- Canadian National Railway (CN)
- Chicago & North Western Railway (CNW)
- St. Charles Air Line Railroad
Strauss Trunnion Bascule
Length of largest span: 220.0 ft.
Total length: 2,000.0 ft.
Approximate latitude, longitude
+41.86110, -87.63456   (decimal degrees)
41°51'40" N, 87°38'04" W   (degrees°minutes'seconds")
Approximate UTM coordinates
16/447332/4634548 (zone/easting/northing)
Quadrangle map:
Inventory numbers
BH 38237 (Bridgehunter.com ID)

Update Log 

  • April 29, 2018: New photos from Drake Krohn
  • April 10, 2018: New photo from Douglas Butler
  • March 28, 2018: New photo from Douglas Butler
  • September 17, 2016: New photo from Dave King
  • August 22, 2016: New photos from Douglas Butler
  • January 27, 2016: New photos from Royce and Bobette Haley
  • January 26, 2016: New photo from Douglas Butler
  • January 19, 2016: New Street View added by Douglas Butler
  • December 14, 2015: Updated by Roger Deschner: Added category "Amtrak"
  • December 14, 2015: New photo from Douglas Butler
  • December 7, 2015: New Street View added by Douglas Butler
  • November 19, 2015: New video from Douglas Butler
  • August 6, 2015: New photo from Douglas Butler
  • October 30, 2014: New photo from Douglas Butler
  • August 26, 2013: New photo from Douglas Butler
  • August 21, 2013: New Street View added by Douglas Butler
  • October 1, 2012: Updated by Daniel Hopkins: Added category "Railroad"
  • September 30, 2012: Updated by Luke Harden: Added category "St. Charles Air Line Railroad"
  • September 29, 2012: Updated by Steve Conro: Added categories "Canadian National Railway", "Navigable waterway"

Related Bridges 



St. Charles Air Line Bridge
Posted January 6, 2018, by Kenny Fairhurst (dwf0403 [at] gmail [dot] com)

To clarify some rumors forming in here...

The bridges do NOT share a counterweight. If that was the case, then both bridges would be operational instead of the CN bridge being the only one operable.

St. Charles Air Line Bridge
Posted August 24, 2016, by george oakley (georgeoakley49 [at] yahoo [dot] com)

Anonymous,that is cool being able to street view along the river.Comes in handy when searching for bridges.

St. Charles Air Line Bridge
Posted August 23, 2016, by Anonymous

You can move on the street view in the map to move along the river. If you look between the two bridges, it looks like they share a control house. The platform and ladder connect the one bridge to the adjacent bridge.

The two separate structures couldn't share a counterweight as they move separately from each other.

St. Charles Air Line Bridge
Posted April 21, 2016, by Nathan Holth (webmaster [at] historicbridges [dot] org)

I've heard others comment that these bridges share a counterweight but I am not sure that's actually what they share if they share anything. Maybe operating equipment? The Air Line Bridge has wing style counterweights and they should not need any supplemental support. In fact they should be overbuilt and may have had to be reduced in weight, since the Air Line Bridge originally was a couple panels longer and when it was moved here it was made shorter. There is no evidence that the counterweights are connected to B&O Bridge... moreover, if they were connected, wouldn't both bridges have to move at the same time? The Air Line Bridge raises and lowers while the B&O stays put. If anyone can clarify the shared counterweight rumor that would be awesome.

St. Charles Air Line Bridge
Posted April 21, 2016, by Shad Vargo (scih30 [at] gmail [dot] com)

Actually I think CSX still owns the B&O portion of the bridge since they cannot abandon that part due to the fact the bridges share a counterweight.

St. Charles Air Line Bridge
Posted January 28, 2016, by Steve Conro (sconro [at] yahoo [dot] com)

Don't get me wrong. If there's an interesting painting, drawing or art of some kind of a a particular bridge. By all means post it. THATS interesting. But 2,3,5,10 of each. If you look at the updates page anymore all you find is 1000's of one persons drawings. One or two of each is plenty.

St. Charles Air Line Bridge
Posted January 28, 2016, by Julie Bowers (jbowerz1 [at] gmail [dot] com)

Given the pen chance for any separate categories....the snapshots in time showing different stages of those bridges are interesting to me. I don't spend a lot of time on that span style, still intrigues.

Art is in the eye of the viewer, those paintings of the past are sure treasures, they say these decades will be the lost ones with no bits to find in the shops of our past. All digital?

I'd like to see those abstracts, never did that style either.

St. Charles Air Line Bridge
Posted January 28, 2016, by ArtS (asuckewer [at] knite [dot] com)

Julie, I absolutely agree! I previously uploaded an image of a painting that hangs in the Metropolitan Museum of Art of a bridge, done in the 1800's, that both conveys more than a period photo would and as there are no photos of that bridge, it represents the only image of a long lost bridge.

That said, as reference, unless they are technical drawings, art is subjective as opposed to objective, which, in my opinion, distracts from the overall bridge entry as a research tool. As an example, I plan on a series of bridge paintings as well. I plan on doing them in the style of Jackson Pollack. While each painting will represent a specific bridge, I highly doubt they would add value to the entry for the bridge as reference documents. Thus my suggestion of a separate category.

Also, my previous post was sincere, I really did break out in laughter when I flipped through all of Douglas' sketches.

St. Charles Air Line Bridge
Posted January 28, 2016, by Julie Bowers (jbowerz1 [at] gmail [dot] com)

Art (and I don't mean Art S) is as valid as any of the photographs. What truly is the problem? Don't look at them if you aren't interested. Can you draw? I do paintings of bridges too, and I've posted a few. I'll start posting some more. At one point I had intended to do a painting for every bridge we do, can't keep up, maybe this will be incentive.

St. Charles Air Line Bridge
Posted January 27, 2016, by ArtS (asuckewer [at] knite [dot] com)

Oh my god! That's awesome! Thanks for the comment, otherwise I would never have looked. I literally laughed when I saw the number of drawings! I didn't realize Douglas did more that one picture per bridge. Now, if we could just convince him to do a new picture of this bridge every day, we'd be all set.

It's too bad we can't have a separate section as a repository of the vast pencil sketch collection - we could have 'guess the bridge' contests :^)


Art S.

St. Charles Air Line Bridge
Posted January 27, 2016, by Steve Conro (sconro [at] yahoo [dot] com)

Enough already with the frigging drawings.