Wyoming Historic Bridges and Tunnels
The landscape of Wyoming is defined by its vast open spaces and rugged terrain, but its history is equally shaped by the engineering feats that connected its remote communities. The National Register of Historic Places recognizes numerous bridges and tunnels across the state that represent the evolution of American transportation and civil engineering.
Of the 41 bridges originally listed on the National Register in Wyoming, only 15 still exist today. This attrition highlights the constant struggle between preserving historical integrity and meeting the demands of modern traffic and safety standards.
ไม่มีภาพประกอบ
Key Facts
- Total Listed: 41 bridges are recognized on the National Register of Historic Places in Wyoming.
- Survival Rate: Only 15 of the original 41 listed bridges remain.
- Common Designs: The state features a variety of truss designs, including Pratt, Warren, Parker, and Pennsylvania styles.
- Diverse Materials: While steel trusses dominate, the list includes specialized structures like the concrete arch of the Hayden Arch Bridge.
Engineering the Frontier: Common Bridge Types
To understand the significance of these structures, it is helpful to recognize the technical terms used to describe their designs. Most of Wyoming's historic bridges utilize truss systems—structures composed of connected elements forming triangular units to distribute weight efficiently.
Through Truss and Deck Truss
A through truss is a bridge where the traffic travels through the structure, with the trussing extending above the roadway. In contrast, a deck truss places the roadway on top of the truss system, leaving the supporting structure beneath the traffic.
Pony Truss
A pony truss is similar to a through truss, but it lacks the overhead bracing. This means the sides of the bridge are not connected at the top, creating a lower profile often used for shorter spans.
Specialized Designs
Wyoming also features more complex designs such as the Pennsylvania through truss, known for its strength over longer spans, and the Camelback design, characterized by a polygonal top chord that resembles a camel's hump.
Notable Historic Structures
From the high plains to the mountain valleys, these bridges served as vital lifelines. Some, like the AJX Bridge over the South Fork and Powder River (built 1931-1932), remain in active use. Others, such as the Hayden Arch Bridge in Park County, showcase the durability of concrete arch construction.
Unfortunately, many structures have been lost. The Bridge over Snake River-Structure DEY in Teton County was removed in 2023, and others like the CQA Four Mile Bridge have been replaced to accommodate modern vehicle weights and volumes.
ไม่มีภาพประกอบ
Summary of Selected Historic Bridges
| Bridge Name | Built | County | Type | Current Status |
|---|---|---|---|---|
| AJX Bridge | 1931-1932 | Johnson | Pratt deck truss | Still in use |
| DMJ Pick Bridge | 1909-1934 | Carbon | Parker through truss | Still in use |
| DSD Bridge | c. 1915-1922 | Niobrara | Pennsylvania through truss | Still in use |
| Hayden Arch Bridge | 1924-1925 | Park | Concrete Arch | Still in use |
| EJZ Bridge | 1925-1926 | Big Horn | Warren pony truss | Still in use |
| ELY Wind River Diversion Dam | 1924-1925 | Fremont | Warren pony truss | Still in use |
Frequently Asked Questions
How many of Wyoming's historic bridges are still standing?
Out of the 41 bridges listed on the National Register of Historic Places in Wyoming, only 15 still exist.
What is the difference between a Pratt and a Warren truss?
While both are truss designs, they differ in the arrangement of their diagonal members. Pratt trusses typically have diagonals that slope toward the center, while Warren trusses use equilateral triangles to spread the load.
Which historic bridge in Wyoming uses a concrete arch?
The Hayden Arch Bridge, located in Park County and built between 1924 and 1925, is a notable example of a concrete arch bridge.
Are any of these historic bridges still used for traffic today?
Yes, several are still in use, including the AJX Bridge, DMJ Pick Bridge, and the DSD Bridge over the Cheyenne River.
What happened to the Bridge over Snake River-Structure DEY?
The Bridge over Snake River-Structure DEY in Teton County was removed in 2023.