• Barnett Bridge and Iron Company - Clinton, IL
• Bellafontaine Bridge and Iron Company - Bellafontaine, Ohio
• Billmire Bridge and Iron Works - Rochelle, Illinois
• Bloomington Bridge and Manufacturing - Bloomington, IL
• Burnham and Ives - Bloomington, IL
• Canton Bridge Company - Canton, Ohio
• Clinton Bridge and Iron Works - Clinton, IL 
• Continental Bridge - Chicago, IL
• Continental Bridge Company - Peotone, IL
• Darst and Hughes Contractors - Chicago, IL
• Decatur Bridge - Decatur, IL
• George Sheldon Company Builders 
• Groton Iron Bridge Builder - Groton, NY 
• H. S. Wetherell Builder - Chicago
• IB&I Company - Sullivan, IL 
• Illinois Bridge Company - Sullivan, IL
• Illinois Steel Bridge Company - Jacksonville, IL
• Indiana Bridge - Muncie, IN 
• Indianapolis Bridge and Iron Works - Indianapolis, IN 
• International Steel and Iron - Evansville, IN
• Iowa Bridge Company - Des Moines, IA
• J. B. Diver and Company - Keokuk, IA
• J. D. Adams - Indianapolis, IN
• J. H. Burham - Bloomington, IL
• J. R. Challacombe - Hillsboro, IL 
• Joliet Bridge and Iron - Joliet, IL 
• King Iron Bridge Company - Cleveland, OH
• M. Bayne and Son - Pekin, IL
• Massilon Bridge Company - Massillon, OH 
• Miles Brothers - Galesburg, IL
• Milwaukee Bridge Company - Milwaukee, WI
• Milwaukee Bridge and Iron Works - Milwaukee, WI 
• Monmouth Bridge and Manufacturing - Monmouth, IL
• New Castle Bridge Company - New Castle, IN
• P. E. Lane Builder - Chicago, IL
• Pan American Bridge Company - New Castle, IN
• Paris Bridge and Supply Company - Paris, IL 
• R. D. Wheaton Bridge Company - Chicago
• Robert Wakefield, Rochelle, Illinois
• Schmitt Construction Company - Tremont, IL
• Smith Bridge Company - Toledo, Ohio 
• St. Louis Bridge and Iron - St. Louis
• Stupp Brothers Builders - St. Louis
• Vincennes Bridge Company - New Castle, IN 
• Wabash Bridge and Iron Works - Wabash, IN 
• Wisconsin Bridge and Iron - North Milwaukee, WI
• Wrought Iron Bridge Company Builder - Canton, OH
• Youngstown Bridge Company - Youngstown, OH

Up to about 1874 the designing and the construction of bridges were almost exclusively in tire hands of the several bridge companies. Each of these companies had its own peculiar style of bridge; consisting of a special form of truss, as the Bollman, Warren and Pratt etc. or in the use of patented forms, as the Phoenix Linville and Piper and American companies' posts and other detailed parts. Each company also had its own special geographical field, or lines of railroad, giving it the preference. Even at points where they did meet as competitors, it was rather as advocates for their special trusses of forms of posts, than as competitors upon any definite specification. Here is a partial list of companies so operating with the truss types built by each:

Name — —  — — Location — —  — Type
American Bridge Co. — Chicago, Illinois — Post
Austin Bridge Co. — Chicago, Illinois — Austin
Berlin Iron Bridge Co. — Berlin, Conn. — Lenticular
Cincinnati Bridge Co. — Cincinnati, Ohio — Whipple
Detroit Bridge & Iron Co. — Detroit, Michigan — Whipple
Hawkins, Herthel & Burral — Springfield, Mass. — Herthal
Kellog Bridge Co. — Buffalo., New York — Whipple
Keystone Bridge Co. — Pittsburgh, Pa. — Whipple
King Bridge Co. — Cleveland, Ohio — King
Louisville Bridge & Iron Co. — Louisville, Ky. — Fink
Phoenix Bridge Co. — Phoenixville, Pa. — Whipple
S. & J. M. Whipple — Utica, K. Y. — Whipple
Wm. Bollman & Son — Baltimore, Md. — Bollman
Canton. Bridge Co. — Canton, Ohio — Post
New York Bridge Co. — New York, N.Y. — Ryder
Chas. Kellogg & Co. — Detroit, Michigan — Bollman