Public Domain: Published Prior to 1923
BH Photo #429518
(Condensing multiple posts into one.)
An 1869 article in the Railway Locomotives and Cars, Volume 42 explicitly states Keystone, and a later publication from the Journal of the Western Society of Engineers and an HAER document on one of the 1870s approaches cite Keystone as the builder of the 1868 spans.
Railway Locomotives & Cars Article (1869):
Journal of the Western Society of Engineers Article (1908):
HAER documentation on a relocated 1870s Pratt:
The photo appears to show Phoenix Columns. Perhaps Keystone Bridge Company erected the bridge, but purchased the Phoenix Columns from Phoenix Bridge Company. Maybe they purchased raw columns and used them for their own fabrication, which might explain the portal looking like Keystone's design. The company did indeed sell the columns individually. Note that the connection detail between columns is unusual, they are not the castings used by Phoenix Bridge Company. This further suggests a possibility that the columns were purchased by Keystone with other bridge fabrication carried out by Keystone. On the other hand, if Keystone did fabricate these columns, we would be looking at a patent violation.
Regardless of builder, these were unique spans. This bridge reused two spans,and there were two spans in Linn County Iowa that were replaced in the 20s. This leaves one or two 1868 spans unaccounted for. With some of the 1870s spans ending up in Mississippi, the unaccounted spans could have ended up virtually anywhere in the central US. However, I doubt they still exist.
I realized that I missed your point - the bridge was manufactured in 1868, relocated in 1900 and washed out in 1911. That timeline makes sense.
It still wasn't made by Keystone :^)
I failed to mention this. The 1872 spans added to the Dubuque bridge were keystone spans. I agree that the spans arenít Keystone. More research is required to find who indeed built the 1860s spans.
The compression members in the photo are Phoenix Columns. Keystone (Carnegie) fought Phoenix all the way up to the Supreme Court regarding the column patents. I highly doubt they would use their competitors products.
The bridge was built using spans relocated from Dubuque, Iowa. They were originally fabricated 1868.
Keystone is unlikely as the builder as the bridge was made using Phoenix Columns. Also, the build date is considerably earlier than 1900.