Paul, here are a few more snippets that may be useful to you:
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A Guide to the Architecture of St. Louis
By Frank Peters, George McCue

A Steel Bridge and Steel Bone Buildings:

EXCERPT: The Eads Bridge completed in 1874, finished river transportation as a serious contender for freight and passenger service, for beneath it's top deck for street traffic was a second deck for railroad traffic

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James Buchanan Eads

http://www.pbs.org/wgbh/amex/eads/peopleevents/p_jbeads.html
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Gay