Scenic Bridge - Tarkio, MT - U.S. National Register of Historic Places on Waymarking.com

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Scenic Bridge - Tarkio, MT

in U.S. National Register of Historic Places

Posted by:  T0SHEA

11T E 678121 N 5210023

About four miles east of Tarkio and ten miles west of Alberton, this truss bridge would have been a major construction project when built in the 1920s.

"Scenic Bridge" is, indeed, an appropriate moniker for this bridge, as it describes not only the bridge but the surroundings, as well. When built in 1927-28, the bridge carried Highway 10 traffic over the Clark Fork River and under a Milwaukee Road Railroad bridge. Here, the river carves its way through a deep and narrow gorge in the valley while the bridge affords an excellent view of both the valley and the railroad bridge.

Originally 18 feet in width and widened in 1951 to 22 feet, the Pratt deck truss bridge consists of no less than seven truss spans, with "four 19-foot steel stringer approach spans, two 77-foot deck truss spans, and a 191-foot steel deck truss main span". In total it is 421 feet in length and, when completed in May of 1928, cost $85,000.

With the construction of I-90, Highway 10 became essentially superfluous, though it remained in use for many years. Today, though the highway remains open, the bridge is closed to all traffic but pedestrians. It remains accessible from both directions but barricades make the bridge itself inaccessible to vehicles.

Scenic Bridge

The Scenic Bridge is an excellent example of a multi-span riveted steel Pratt deck truss bridge. The bridge was built from standardized designs developed by the Montana Highway Department about 1927 specifically for this bridge.

The Scenic Bridge is a seven-span, riveted steel Pratt deck truss structure. Four of the spans are steel stringer approach spans. The bridge rests on concrete abutments and piers. The bridge is 421 feet long and consists of four 19-foot steel stringer approach spans, two 77-foot deck truss spans, and a 191-foot steel deck truss main span. The bridge is 25 feet wide with a roadway width of 24 feet. Located in the spectacular Alberton Gorge of western Montana, the deck of the bridge is situated about 104 feet above the average level of the Clark Fork River. A Milwaukee Road Railroad bridge passes 15 feet above one of the 77-foot span of the Scenic Bridge further adding to the picturesque appearance of the bridge in a spectacular river gorge. The substructure of the bridge consists of two reinforced concrete open hammerhead-type abutments and six reinforced concrete piers . All are solid structures with two extended cylindrical caps upon which the trusses rest. Each pier consists of two concrete columns connected by a concrete web wall. Each pier has a cylindrical extended cap.

In early 1926, the Mineral County Commissioners condemned the bridge near Cyr and called for a special bond election to raise matching money to construct a new bridge across the river. The election succeeded by only eighteen votes. State Highway Commission Bridge Engineer Walter P. Wesch designed a 7-span riveted Pratt deck truss to span the crossing in the gorge. On June 24, 1927, the Montana State Highway Commission let the contract to the William P. Roscoe Company of Billings. The Highway Commission estimated the cost of construction at $73,856.42, but Roscoe underbid the estimate by $6,714.22, submitting a proposal for $67,142.20. Work began on the bridge in the late summer of 1927. Because of problems with the foundation of the bridge, the cost of the structure eventually rose to more than $85,000 to complete. The difference between the contractor's estimate and the final cost was made up through State Highway Commission force account. Roscoe completed the structure in early May 1928.

The Scenic Bridge was associated with the development of US Highway 10 through western Montana as not only a commercial route, but also as a scenic route to draw tourists to the area. The bridge is located in a spectacular river gorge immediately beneath a Milwaukee Road Railroad structure. Because of its location and picturesque qualities, local promoters christened it the "Scenic Bridge" as a way to advertise the area's natural beauty. The bridge was one of four riveted Pratt deck truss bridges built by the Montana Highway Commission between 1928 and 1932. All four were located in river canyons on heavily traveled highways. Although altered in 1951 and 1965, the bridge is an excellent example of the type and one of the most well-known bridges in Montana.
From the NRHP Nomination Form