Bridge conditions in Hamilton County, Iowa
165 inventoried bridges · 32 rated poor · 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
Hamilton County has 32 bridges rated poor out of 165 inventoried, a 19.4% share that puts it well above the national rate of about 7%.
- 32 of the 165 bridges in Hamilton County, Iowa, are rated in poor condition (19.4%) in the 2025 National Bridge Inventory, as of .
- 61 bridges (37.0%) are rated good and 72 (43.6%) fair.
- The median Hamilton County bridge was built in 1972.
- The busiest poor-rated bridge is FM over Skunk River (built 1974), carrying about 698 vehicles a day.
Good 37.0% · Fair 43.6% · Poor 19.4% of 165 bridges
Bridges rated poor
Every bridge in the county with a poor rating, busiest first. Poor means a major component is rated 4 or lower on FHWA's 0-9 scale; it is a repair flag, not a closure notice.
Busiest bridges in the county
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 35 over Drainage Ditch | 1966 | 27,200 | Fair |
| I 35 over Stream | 1965 | 26,900 | Good |
| I-35 over Tuttle Creek | 1967 | 17,400 | Fair |
| I-35 over Drainage Ditch 23 & 31 | 1972 | 16,600 | Good |
| I 35 NB over Ia 175 | 1966 | 11,850 | Fair |
| I 35 SB over Ia 175 | 1966 | 11,850 | Fair |
| US 20 & Ia 17 over Waterway | 1977 | 11,200 | Fair |
| US 20 over Drainage Ditch #4 | 1968 | 9,600 | Good |
| US 20 over Drainage Ditch #4 | 1968 | 9,600 | Fair |
| US 20 over Drainage Ditch #4 | 1968 | 9,600 | Good |
Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.
Every bridge in Hamilton County → - all 165, busiest first, each with its own condition record.
All of Iowa: Iowa bridge conditions by county · every download on the data page.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.