Ill 75 over Rock River
Winnebago County, Illinois · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Ill 75 over Rock River in Winnebago County, Illinois, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1927 and reconstructed in 1974, making it 98 years old at the 2025 inventory.
- It carries about 7,200 vehicles a day (traffic count year 2023).
- Its listed owner is the state highway agency.
- It is one of 291 of the 465 inventoried bridges in Winnebago County rated fair (62.6%); 32 (6.9%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated June 2024, on a 24-month routine inspection cycle.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (42.44928, -89.07248)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 5 | 5 | Fair condition |
| Superstructure | 5 | 5 | Fair condition |
| Substructure | 5 | 5 | Fair condition |
Bridge details
| Structure | Continuous prestressed concrete stringer or multi-beam girder |
| Length | about 568 ft |
| Location | In Rockton |
| NBI structure number | 101010900000000 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | June 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 5: foundations stable, scour within the limits of the footing or piles |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Illinois department of transportation.
Busiest bridges in Winnebago County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I-39 & US 20 over Madigan Creek | 1963 | 50,900 | Fair |
| I-90 N B over US 20 Br | 2009 | 36,350 | Good |
| I-90 S B over US 20 Br | 2009 | 36,350 | Good |
| US 20 W B over Ill 251 (11TH St) | 1960 | 36,000 | Fair |
| I-90 over Stream | 1958 | 34,100 | Good |
| US 20 E B over Kishwaukee St. | 1960 | 32,000 | Fair |
All bridges nearby: Winnebago County, IL bridge conditions · every bridge in Winnebago County · Illinois bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.