Bridging the River - Thompson Falls, MT
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T0SHEA
N 47° 35.462 W 115° 21.284
11T E 623694 N 5272158
1911 was this bridge's birth year and 2010, 99 years later, was the year of its rebirth. According to Morrison-Maierle, Inc., engineers for the rehabilitation, this is the last Parker-Pratt Deck Truss bridge remaining in Montana.
Waymark Code: WMN1K3
Location: Montana, United States
Date Posted: 12/07/2014
Views: 1
This was one of a pair of bridges built to support construction of the Thompson Falls Hydro Dam Project, also of 1911 vintage. Originally a vehicle bridge, the Parker-Pratt deck truss bridge served areas to the south of the Clark Fork River until its closure due to deterioration in 1979. It is 80 feet high and 588 feet long.
The only bridge of its kind in Montana still standing, it was entered in the National Register of Historic Places in 1986 as a contributing structure to the Thompson Falls Hydroelectric Dam Historic District.
High Bridge Facts
Longest bridge of its kind still standing in Montana.
Included on the National Register of Historic Places in 1986 as part of the "Hydroelectric Dam Historic District".
Length: 588 feet
Style: Parker/Pratt Deck Truss
Deck Width: Originally 18 feet wide: reconstructed to 12 feet wide.
Spans:
(1) 55-foot, 3-panel Parker Deck Truss
(1) 160-foot, 9-panel Pratt Deck Truss
(2) 127-foot, 7-panel Pratt Deck Trusses
(1) 65-foot, 4-panel Pratt Pony Truss converted to a Deck Truss
(3) Wood stringer spans replaced by one steel span during renovation
Bridging the River
To assist construction of hydroelectric projects, Sanders County built two bridges in 1911 that linked the north and south shorelines of the Clark Fork River across Thompson Falls Island. Near you is the 588-foot-long High Bridge, which connects the island to the south shoreline. The 377-foot-long Gallatin Street Bridge (formerly known as the Dry Channel Bridge) links the island to the north shore.
The bridge route across Thompson Falls Island was the main transportation thoroughfare until 1928, when a bridge was built over the Clark Fork River west of Thompson Falls at Birdland Bay. The island route's usefulness was further diminished in 1961, when the State Highway 200 Bridge was built just 11/2 miles downstream. Due to deterioration, the High Bridge was closed to vehicular use in the early 1970s and then to all use in the late 1970s—breaking the link across the Clark Fork River at Thompson Falls. The Gallatin Street Bridge remained open for public non-motorized access to the island and operation of the Thompson Falls Project's dams.
New life was given to the High Bridge after interest grew in re-establishing the connection between the City of Thompson Falls and the river's south shoreline. Through the efforts of Sanders County and numerous individuals, organizations and agencies, the High Bridge was renovated and reopened for pedestrian and bicycle use in May 2010. After lying idle for more than 30 years, the High Bridge now serves the area's recreational and non-motorized transportation needs.
From the Plaque