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A18 (140TH St) over Big Sioux River

Lyon County, Iowa · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

A18 (140TH St) over Big Sioux River in Lyon County, Iowa, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 5 (fair condition) on the 0-9 scale.
It was built in 1963, making it 62 years old at the 2025 inventory.
It carries about 1,607 vehicles a day (traffic count year 2022).
Its listed owner is the county highway agency.
It is one of 99 of the 273 inventoried bridges in Lyon County rated fair (36.3%); 70 (25.6%) are rated poor.
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.

Component ratings


Structure	Continuous steel stringer or multi-beam girder
Length	about 400 ft
Location	100493503
NBI structure number	000000000231610
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the Iowa department of transportation.

Bridge	Built	Vehicles/day	Condition
Ia 9 over Stream	1980	4,840	Good
Ia 9 over Stream	1940	4,520	Fair
Ia 9 over Bloodrun Creek	1977	4,520	Fair
US 75 & Ia 9 over Moon Creek	1972	4,400	Fair
Ia 9 over Rock River	1974	3,920	Fair
Ia 9 over Mud Creek	1975	3,270	Fair