From Illinois Highways, Volumes 2-4
Public Domain: Published Prior to 1923
View this photo at books.google.com
BH Photo #340657
To follow up on my comments, you can see a source historical article here: http://historicbridges.org/bridges/browser/?bridgebrowser=il...
Jason, it isn't a mystery, its just an interesting and apparently little-known history. J. C. Darst in 1881 formed a "copartnership" with A. J. Sprague operating as the Massillon Bridge Works (previously started by Joseph Davenport). In 1883 Darst moved to Chicago, and operated the western business for the firm. In 1900 when Massillon Bridge was reorganized and became the Toledo Massillon Bridge Company, Darst left the formal association and formed a contracting firm of Darst and Hughes of Chicago. A 1904 plaque in Iroquois County shows that Darst and Hughes still operated at that date as agents for Massillon Bridge Company: http://bridgehunter.com/il/iroquois/38413709090/
Darst and Hughes was later reincorporated as the Continental Bridge Company (perhaps ca. 1905) with Darst acting as treasurer until his death in 1907.
So long story short, J. C. Darst was an influential figure in both Continental Bridge and Massillon Bridge, with Continental Bridge Company basically being the independent successor to the Massillon Bridge Company. I am not sure if they continued buying bridges from Massillon or if they fabricated their own, simply copying Massillon designs and plaques. As for the Massillon designation for THIS bridge, I make the assumption that the provided 1902 construction date is accurate. Assuming it is, this bridge should be a Massillon product.
Is it a Massillon? Doubtful for it could also be a Continental Bridge Company product. Read this mystery article to see why and decide which bridge builder put this structure together: http://thebridgehunter.areavoices.com/2015/10/27/mystery-bri...