The bridge span collapse we think might've occurred in 1970 or 1971. The train was carrying a load of government brass (either to or from the Joliet Arsenal, perhaps?) which ended up in the Kankakee. GIs were sent to guard the site until the brass could be recovered. James Holzmeier, Wabash RR Hist. Soc.
Hint of a wreck in 1968. Perhaps some of the N&W railfans could provide details.
Info on Gretz:
Big Maps has a very nice view of this bridge:
http://www.bing.com/maps/?v=2&where1=41.24571%2C%20-88.12765...
Click on Bird's Eye view
I scanned this postcard for you
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