1 vote

370th Street Bridge


Iowa Department of Transportation


BH Photo #270770

Street View 


Located southwest of Henderson in northwestern Mills County, this rigid-connected pony truss carries a paved county road (once a part of a state highway) over the Nishnabotna River. The bridge is comprised of two skewed trusses, each configured as a Warren pony with polygonal upper chords. The trusses are supported by concrete abutments and piers, and they are approached by steel stringer approach spans on both ends. The Nishnabotna River Bridge was designed by engineers for the Iowa State Highway Commission in the summer of 1929. The bridge's skewed orientation and relatively long span length prompted ISHC to produce a special design for the trusses, rather than rely on its standard plans. On August 20, 1929, the state highway commission contracted with the McCormack Construction Company of Lohrville, Iowa, to construct the bridge for $30,900. Using steel rolled by Inland, McCormack completed the bridge the following year. It has since functioned in place, without substantial alteration. Although at least one Iowa bridge company employed polygonal-chorded Warren trusses on a limited basis in the early 1910s, this inherently long-span structural type never found much favor among the counties. As a result, relatively few such trusses were built in the state between 1910 and 1913--the year that the state highway commission began issuing standard plans for bridges. ISHC's standard pony trusses ranged in span length between 35 and 100 feet, all featuring straight-chorded Warren configurations. The sloped upper chords of the Nishnabotna River Bridge are an anomaly, apparently an attempt by ISHC to develop a more materially conservant structural type for its long-span ponies. It is not known whether the Nishnabotna River Bridge was the first example of this truss type, or whether others were ever built, but this bridge is today is distinguished as the only example of its kind by ISHC remaining in the state. It is thus technologically noteworthy as a well-preserved example of an uncommon structural type [adapted from Fraser 1990].


Pony truss bridge over Nishnabotna River on 370th Street
Mills County, Iowa
Replaced by a new bridge
Built ca. 1940
- Inland Steel Co. of East Chicago, Indiana (Steel mMnufacturer)
- Iowa State Highway Commission of Ames, Iowa (Designer)
- McCormack Construction Co. of Lohrville, Iowa
Riveted warren pony truss
Length of largest span: 100.1 ft.
Total length: 291.0 ft.
Deck width: 19.7 ft.
Posted to the National Register of Historic Places on May 15, 1998
Approximate latitude, longitude
+41.08846, -95.48022   (decimal degrees)
41°05'18" N, 95°28'49" W   (degrees°minutes'seconds")
Approximate UTM coordinates
15/291680/4551541 (zone/easting/northing)
Quadrangle map:
Land survey
T. 73 N., R. 40 W., Sec. 29
Average daily traffic (as of 2016)
Inventory numbers
IA 246630 (Iowa bridge number)
NRHP 98000496 (National Register of Historic Places reference number)
BH 14034 (Bridgehunter.com ID)
Inspection report (as of March 2017)
Overall condition: Poor
Superstructure condition rating: Serious (3 out of 9)
Substructure condition rating: Critical (2 out of 9)
Deck condition rating: Serious (3 out of 9)
Sufficiency rating: 26.1 (out of 100)
View more at BridgeReports.com

Update Log 

  • May 1, 2017: Added by Bill Martin
  • November 20, 2013: New photo from Luke Harden
  • March 12, 2012: Updated by Luke Harden: Added category "Iowa State Highway Commission"
  • July 30, 2011: New photo from Luke Harden
  • July 29, 2011: Updated by Luke Harden: Added description and photograph, updated bridge type



Nishnabotna River Bridge
Posted October 21, 2021, by Luke

As Dave King pointed out years ago, this is a duplicate.

Nishnabotna River Bridge
Posted May 2, 2017, by Nathan Holth (webmaster [at] historicbridges [dot] org)

This bridge would be a great candidate for reuse. The SHPO should consider waiving the requirements if nobody steps forward agreeing to all of their conditions. The SHPO should rather see this bridge preserved even without National Register Listing, instead of being scrapped and turned in to Chicken Noodle Soup cans...

Nishnabotna River Bridge
Posted May 2, 2017, by Tony Dillon (spansaver [at] hotmail [dot] com)

Dismantle and store requirements need to be in place for all historic bridges that are to be replaced... Five to ten years minimum.

Yes Julie, it sounds like Iowa waits until the last minute and then expects a miracle!

Nishnabotna River Bridge
Posted May 2, 2017, by Robert Elder (robertelder1 [at] gmail [dot] com)

From my personal observation, I would say that by the time a state (any state) or county has already made the decision to replace a bridge, it is usually too late to save it without great difficulty.

It is also difficult to come up with a large amount of money at the last minute in order to save a bridge that is just about to face the wrecking ball. (ie. demolition contract already signed).

Simply put, bridges present a lot of challenges for SHPOs that other structure simply don't present. Let's face it, a historic 1855 tool shed does not have to carry ambulances and fire trucks over an active river. Bridges do. Thus, the metal truss bridge is probably one of the most endangered types of historic structures in the United States.

This is why advocacy in advance is so important and often effective. If we want to save our favorite bridges we need to plan for saving them well in advance. Photographing bridges is fun, but advocating for them is absolutely necessary. We cannot wait to act until the construction company is already cutting down the trees around our favorite bridge.

I really have to admire folks like Julie who have built their companies from the ground up. This is a hard business but I do believe it can be a rewarding one.

Nishnabotna River Bridge
Posted May 2, 2017, by Julie Bowers (jbowerz1 [at] gmail [dot] com)

I would think about offering to save these bridges but IOWA SHPO truly makes it way too hard. You must know what you're doing, you must have all the money, you must make sure it has somewhere to go that they like and none of it must come back to them, oh and figure out your own scope of work and estimates.

Other states do it better. This just makes me laugh out loud. They have learned nothing except that in order to fulfill the mission they have to offer it up for sale and do a historic bridge plan.

We can find homes for Warren pony trusses but we won't know until we get them, see what restoration needs are and then find the new homes. It is just backwards.

Nishnabotna River Bridge
Posted May 1, 2017, by EOR_Iowa (bmartin [at] eorinc [dot] com)

The correct date is May 19th, not June 28th, to respond to listing.

Nishnabotna River Bridge
Posted May 1, 2017, by Robert Elder (robertelder1 [at] gmail [dot] com)

The comments and images on this page provide some great information. Perhaps the Webmaster can merge this information with the original page.

Reuse of this bridge sounds like a great idea. Thanks to all for calling to our attention.

Nishnabotna River Bridge
Posted May 1, 2017, by Dave King (DKinghawkfan [at] hotmail [dot] com)
Nishnabotna River Bridge
Posted May 1, 2017, by Bill Martin (bmartin [at] eorinc [dot] com)

Mills County is making the Nishnabotna River Bridge available for sale to allow it to be moved to a different site and preserved for future generations. The bridge spans the West Nishnabotna River and is currently located on County Road M-16 (370th Street) approximately 4.6 miles northeast of Hastings and 4.2 miles south of Henderson in the northeast portion of Mills County, Iowa. The bridge was listed on the National Register of Historic Places in 1998. Plans are currently being made to construct a new bridge meeting current design and safety standards at this location.

The historic Nishnabotna River Bridge is a 291 x 20, 4 span, steel Warren pony truss bridge. The existing bridge is currently open to traffic. The new bridge will be placed along the existing alignment.

Any parties interested in purchasing the bridge must be able to prove they have: 1) the intention to preserve the historical integrity of the bridge, 2) the means to remove and relocate the bridge, 3) a predetermined location to place or store the bridge, and 4) the means to conduct necessary maintenance to return the bridge to adequate public safety standards.

Any party who purchases the bridge should make a good faith effort to place the bridge in a setting similar to its original environment, to reconstruct the bridge in such a way that the historic character of the bridge is still apparent, and to re-list the bridge on the National Register of Historic places.

Interested parties will be given until June 29, 2017 to respond to this advertisement. If the County receives no offer that it determines conforms to the requirements above, the County, in consultation with Iowa State Historic Preservation Office, may demolish the property.