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Ellsworth Ranch Bridge

Iowa Bridge Number 148950

Ellsworth Ranch Bridge

Primary Photographer(s): Nathan Holth and Rick McOmber

Bridge Documented: July 1, 2009

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Key Facts

Facility Carried / Feature Intersected
130th Street Over East Fork Des Moines River
Location
Rural: Emmet County, Iowa: United States
Construction Date and Builder / Engineer
1895 By Builder/Contractor: King Bridge Company of Cleveland, Ohio

Technical Facts

Rehabilitation Date
1937
Main Span Length
80 Feet (24.38 Meters)
Structure Length
80 Feet (24.38 Meters)
Roadway Width
15 Feet (4.57 Meters)
Spans
1 Main Span(s)
NBI Number
148950

Historic Significance Rating (HSR)

Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

View Historic American Engineering Record (HAER) Documentation For This Bridge

HAER Data Pages, PDF

View The Original Thacher Patent That This Truss Is Similar To

Some sources have classified this bridge as a Warren truss variant, however this bridge is more appropriately and clearly categorized and recognized as a Thacher truss. The issues with classifying this bridge likely have cropped up because of the history of the Thacher truss as a configuration. Thacher truss bridges defy precise classification and configuration because the Thacher truss was a patented truss configuration that bridge companies could not copy exactly. As a result, they designed bridges that were extremely similar to the Thacher patent truss configuration but which were different enough so as to be protected from infringement. No bridges survive that directly follow the Thacher patent truss... in other words bridges built by Edwin Thacher or the Keystone Bridge Company for which he worked. Other surviving Thacher truss bridges left standing  and also the Ditch Road Bridge, were built by the Wrought Iron Bridge Company of Canton, Ohio, and this Ellsworth Ranch Bridge was built by the King Bridge Company of Cleveland, Ohio under the auspices of regional agent Milo Adams. The difficulties in classification are apparent by comparing the Ellsworth Ranch Bridge to the aforementioned Ditch Road Bridge. Both have diagonal members that form the distinctive single "W" shape that spans from endpost to endpost, with the outer diagonals being tension members, and the center members being compression members. However Ditch Road Bridge contains a series of vertical members throughout the truss, while the Ellsworth Ranch Bridge only has hip verticals, with no other verticals present. Despite these differences, all are today considered Thacher trusses because of their extreme significance as one of the rarest surviving truss configurations in the country. Nationwide, only a few examples remain. As such, each surviving example, including the Ellsworth Ranch Bridge, should all receive the highest preservation priority possible.

This bridge was fabricated by the King Bridge Company of Cleveland, Ohio. The actual bridge design was engineered by the King Bridge Company's agent for the region, Milo A. Adams. The bridge design appears to have been the brainchild of Adams alone, and was never adopted by the King Bridge Company as a whole. Milo A. Adams later formed his own company in Minneapolis, called simply Milo A. Adams Bridge Company.

The Ellsworth Ranch Bridge is perhaps the most unique of the surviving Thacher truss bridge designs because in addition to its rare truss design, it features extremely unusual design details that are very bizarre. Perhaps the most obvious and extremely unusual detail is the arrangement of the built-up top chord and endpost, which is configured with front-to-front channels with v-lacing on the sides. The visual appearance of connections along the top chord and end post have an unusual appearance as well as a result of this design. Also, the center two diagonal members, which are compression members and thus not eye bars, are rigidly connected with rivets rather than pin-connected. This combination of riveted and pinned connections, especially with a pre-1900 bridge is noteworthy. The overall design and configuration of the bridge is very lightweight and was designed with economy of materials in mind.

This bridge is seated on caissons (sometimes called Lally columns), consisting of concrete-filled metal tubes.

While this abandoned bridge appears to remain in good condition and appears to be unthreatened in its current location, this bridge would also make a great candidate for relocation and restoration for pedestrian use in a park or on a non-motorized trail. In its current location, the bridge is difficult for the public to enjoy, since the bridge is positioned in the middle of field with tall grass that is liberally infested with ticks. Either way, this bridge should be protected from damage, demolition, collapse, etc. at all costs, whether that means simply leaving it standing where it is, or relocating and restoring the bridge. Given  Iowa's tendency to have floods, it is worth a warning that great efforts should be taken to ensure that this bridge is in no danger whatsoever from flood damage. There would be more surviving Thacher truss bridges, if Michigan had not hired an inept engineer to relocate the Ditch Road Bridge onto low piers that were not designed for flood waters.

Information and Findings From Iowa's Historic Bridge Inventory

Discussion of Bridge

Located in northeastern Emmet County, this short-span through truss extends north-south across the East Fork of the Des Moines River. The structure consists of a single pin-connected truss, supported by steel cylinder piers, with timber retaining walls. The five-panel truss displays elements of both Pratt and Warren configurations. The end posts and outside panels are typically Pratt-like, but the interior three panels feature a triangular, Warren-like configuration, with diagonals acting alternating in compression and tension. Even in this, the truss's web differs from the typical Warren configuration, however, because the inverted V of the center panel diagonals does not parallel the diagonals in the adjacent panels. Known locally as the Ellsworth Ranch Bridge, this structure dates to 1895. In January of that year the Emmet County Board of Supervisors received a petition for a bridge across the Des Moines River in Lincoln Township. The board laid the matter over until April, whereupon it approved construction of the bridge and solicited competitive bids for its fabrication and erection. When the proposals were submitted the following month, the board adopted the plans of King Iron Bridge Company as "the most suitable," but rejected all of the bids as too high. After further discussion, the supervisors rewrote the specifications for the proposed bridge, reducing its length from 100 feet to 80 feet in the hope that the reduction in materials would result in a lower cost. This strategy was apparently successful. By the day's end, the supervisors had awarded a contract to the King Iron Bridge Company for the construction of three bridges - including this truss--for $3,400. The Ellsworth Ranch Bridge was completed later that year. Other than a minor reconstruction in 1937, it remains unaltered today.

The Pratt and Warren truss configuration were both developed in the 1840s, but it was the Pratt that received the most widespread use in the late 19th century. The reasons for this probably relate to the versatility of the pin-connected Pratt for different span lengths and its easier erection using timber falseworks. The Ellsworth Ranch Bridge represents an unusual hybridization of Warren and Pratt technologies. It is identical in size and detail with two such trusses found in South Dakota, both built in the mid-1890s by the King Bridge Company, as represented by King's Minneapolis representative, M.A. Adams. This esoteric truss does not appear in company literature of the time, suggesting that its use was experimental and short-lived. The only one of its type identified in Iowa, the Ellsworth Ranch Bridge is thus a rare surviving example of structural experimentation by one of the country's most prolific 19th-century bridge manufacturers [adapted from Fraser and Lauber 1992].

Bridge Considered Historic By Survey: Yes

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