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172ND St over Okobojo Ck

Sully County, South Dakota · rated Fair in the 2025 National Bridge Inventory

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

172ND St over Okobojo Ck in Sully County, South Dakota, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the substructure, rated 5 (fair condition) on the 0-9 scale.
It was built in 1912 and reconstructed in 1967, making it 113 years old at the 2025 inventory.
It carries about 25 vehicles a day (traffic count year 2022).
Its listed owner is the county highway agency.
It is one of 11 of the 31 inventoried bridges in Sully County rated fair (35.5%); 6 (19.4%) 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	Steel stringer or multi-beam girder
Length	about 30 ft
Location	4N & 2.9W Agar
NBI structure number	000000060281000
Condition class	Fair

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

Bridge	Built	Vehicles/day	Condition
US083 over Okobojo Ck	1998	1,490	Good
185 St over Ck	2017	760	Good
SD1804 over Cow Ck	2007	632	Good
SD1804 over Okobojo Ck	1972	632	Fair
SD1804 over Ck	1995	261	Good
291 Avenue over Okobojo Ck	1936	250	Fair