Historic Bridges in Idaho
354 bridges built before 1951 in Idaho still in service today.
Bridges Built Before 1951
The United States has 354 bridges in Idaho built before 1951 that remain in active service. These structures are 75+ years old — many predate modern engineering codes and were not designed for today's traffic volumes and vehicle weights. The average design life of a bridge is 50 years, making these aging structures a significant infrastructure concern.
| Bridge | State | Condition | Year Built | Age (Years) | ADT |
|---|---|---|---|---|---|
| SWAMP CREEK | Idaho | Fair | 1950 | 76 | 30 |
| HOODOO CREEK | Idaho | Good | 1950 | 76 | 30 |
| NORTH FORK WOOD RIVER | Idaho | Poor | 1950 | 76 | 50 |
| VALLEY CREEK | Idaho | Poor | 1950 | 76 | 50 |
About Historic Bridge Data
Bridges built before 1951 are classified as historic in this database. Many were designed to 1940s standards with lower load limits and narrower lanes. While FHWA requires regular inspections of all bridges regardless of age, older structures often require more frequent monitoring and rehabilitation investment.