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181ST Street over Big Sioux River

Hamlin County, South Dakota · rated Good in the 2025 National Bridge Inventory

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

181ST Street over Big Sioux River in Hamlin County, South Dakota, is rated in good condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 7 (good condition) on the 0-9 scale.
It was built in 2016, making it 9 years old at the 2025 inventory.
It carries about 66 vehicles a day (traffic count year 2022).
Its listed owner is the county highway agency.
It is one of 26 of the 61 inventoried bridges in Hamlin County rated good (42.6%); 7 (11.5%) are rated poor.
A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.

Component ratings


Structure	Prestressed concrete stringer or multi-beam girder
Length	about 96 ft
Location	2N & 1.2W of Castlewood
NBI structure number	000000029218030
Condition class	Good

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

Bridge	Built	Vehicles/day	Condition
I029 S over 462 Ave	1973	4,595	Fair
I029 N over 462 Ave	1973	4,595	Fair
I029 S over Stray Horse Ck	1973	4,595	Fair
I029 N over Stray Horse Ck	1973	4,595	Fair
I029 S over SD022	1973	4,595	Fair
I029 N over SD022	1973	4,595	Fair