The one thing we can all agree on is that nobody in the area pronounces it "Kigh-row" as in Egypt's Cairo.
I was thrilled to see this article! One of the prizes in my library of resources on bridges and trestles is the Final Report by Modjeski and Masters addressed to Mr C.H. Mottier, VP and Chief Engineer of the Illinois Central, on the construction of that bridge, dated June 1, 1953, and hard-bound. It is filled with drawings, and some photos (including the entire sequence of launching Span 2 into the water), and a great deal of technical (and cost) data about materials (including mill, forge, foundry and shop inspection info for the steel), sources of supply, soundings, soil borings, tensile strength and other such engineering matters, and technical drawings with time lines and other information. There is a reasonably non-technical narrative of the building and design process (including info on the prior bridge) but the article is easier for a non-engineer like me to follow.
I have not re-read the entire report to see if it discusses this small building, but at one point under Superstructure it does say "The contractor began assembling crews and equipment on April 24, 1950. Preliminary work included the erection of a field office....