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.

Clear
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.