4 votes

Otranto Bridge


Photo taken by Jason Smith in August 2011


BH Photo #212332


Street View 


The Otranto Bridge carries an abandoned county road across the Big Cedar River just east of the hamlet of Otranto in Mitchell County. On January 3, 1899, the Chicago Bridge and Iron Company signed a contract with the Mitchell County Board of Supervisors to build two bridges near Otranto and Osage for the aggregate sum of $5,000. The Otranto Bridge accounted for $3,257 of that amount. CB&I was established in 1899 by Horace E. Horton, a civil engineer who first began building iron and steel bridges for Mitchell County during the late 1870s, while practicing in Rochester, Minnesota. The Otranto Bridge illustrates Horton's penchant for the unusual in his truss design. A Camelback through truss with subdivided panels, this structure is supported by concrete and stone abutments and features pinned connections throughout. Functioning in place today, the Otranto Bridge is a structurally sound example of this peculiar bridge configuration. Straight-chorded Pratt through trusses were used extensively throughout Iowa for medium-span crossings in the late 19th and 20th centuries. For longer crossings, however, bridge companies could develop greater efficiency with polygonal-chorded Pratt variants-primarily Parker, Pennsylvania and Camelback trusses. With its distinctive five-faceted upper chords, the Camelback configuration was disdained by some engineers (including the redoubtable J.A. L. Waddell, who called it "uncompromisingly ugly") for its tendency under certain circumstances to reverse compressive and tensile forces acting non their individual members. As a result, Camelback trusses never received widespread acceptance. Relatively few were ever built on Iowa's roads, and only a handful has survived to the present. The Otranto Bridge is technologically significant as a well-preserved example of this uncommon Pratt variant [adapted from Lauber 1992]


Abandoned Camelback-Pennsylvania through truss bridge over Big Cedar River on 480th Avenue
Otranto, Mitchell County, Iowa
Future prospects
Bridge is privately owned
Built 1899
- Chicago Bridge & Iron Co. of Chicago, Illinois
Pin-connected Camelback through truss
Length of largest span: 140.1 ft.
Total length: 207.0 ft.
Deck width: 15.4 ft.
Posted to the National Register of Historic Places on May 15, 1998
Approximate latitude, longitude
+43.45804, -92.98163   (decimal degrees)
43°27'29" N, 92°58'54" W   (degrees°minutes'seconds")
Approximate UTM coordinates
15/501486/4811681 (zone/easting/northing)
Quadrangle map:
Saint Ansgar
Inventory numbers
IA 248060 (Iowa bridge number)
NRHP 98000495 (National Register of Historic Places reference number)
BH 43693 (Bridgehunter.com ID)

Update Log 

  • March 13, 2014: Updated by Luke Harden: Removed
  • July 22, 2013: New photos from Julie Bowers
  • June 8, 2012: Updated by Jason Smith: This bridge is a Pennsylvania Petit with Camelback features
  • September 5, 2011: New photos from Jason Smith
  • July 19, 2011: Updated by Jason Smith: Added GPS coordinates
  • December 1, 2009: Added by Jason Smith


  • Jason Smith - flensburg [dot] bridgehunter [dot] av [at] googlemail [dot] com
  • Julie Bowers - jbowerz1 [at] gmail [dot] com
  • Luke


Otranto Bridge
Posted March 13, 2014, by Jason Smith (JDSmith77 [at] gmx [dot] net)
Otranto Bridge
Posted March 12, 2014, by ArtS (asuckewer [at] knite [dot] com)
Otranto Bridge
Posted August 10, 2013, by Julie Bowers (jbowerz1 [at] gmail [dot] com)
Otranto Bridge Design
Posted July 22, 2013, by Fmiser (fmiser [at] gmail [dot] com)

What to call it...

The top chord is composed of five straight sections, so it qualifies as a camelback something.

There are diagonals that span two verticals, so either it is "double-intersecting" or "sub-divided".

Since some of the diagonals don't span from the top to the bottom chord, it meets the definition of "sub-divided".

Except, as Julie said, the sub-divisions are at the top chord, not the typical bottom chord.

So, I guess I would call it a "Camelback pratt truss with inverted sub-divisions". Or "Camelback pratt truss with upper sub-divisions".

That's my opinion, anyway. *smiles*

Otranto Bridge
Posted July 22, 2013, by Julie Bowers (jbowerz1 [at] gmail [dot] com)

I am still trying to figure out the truss design on this. HAER says Camel Back with subdivided panels, Jason Smith has added Pennsylvania Petit to the features. I have done a sketch and the subdivided panels are exactly opposite the Pennsylvania diagram I was looking at. Any other folks want to weigh in on this. I would like to be able to call it something other than "uncompromisingly ugly" which the HAER report also goes into.

I think it would be a great Farmer's Market and open air garden. A money maker for a non-profit.

Could be repaired and sold to county as part of their park just upstream past the new bridge. (people use it that way anyway, including the point where they fish and launch boats).

Could be pulled and stored, pulled and moved or pulled and scrapped (last choice of private home owner).

Any other opinions as to truss type and use always greatfully appreciated. Here is a little sketch I did to help my own understanding of how this works. Eyebars on all diagonals and 1st verticals. Riveted and laced full & half verticals at every panel, floor beams and 21 pin connections.

Attachment #2 (application/pdf; 1,171,686 bytes)

Otranto Bridge
Posted July 16, 2013, by Don Morrison


Bypassed in 1979. I hope it can be saved. It's one of the last through trusses still standing in Mitchell County.

The Cedar seems to get wild every spring lately. Moving it to span a smaller stream for preservation might be the safest thing for it. Expensive, though.

Otranto Bridge
Posted July 16, 2013, by Julie Bowers (jbowerz1 [at] gmail [dot] com)

I am going to visit this bridge today. The new owner thought it would be great to own a bridge with his property. Recent flooding caused some scouring to an abutment and the county has been declared a disaster. He approached a house moving company to see about moving the bridge but that was a high bid. Now we are going in to see if there are any new ideas that we can bring to the table. It was bypassed, that doesn't happen often in Iowa.

Another use? pull and disassemble? pull and scrap? always the same old questions but when these reach private hands they are hard to save.