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Bridge conditions in Corson County, South Dakota

49 inventoried bridges · 4 rated poor · 2025 National Bridge Inventory

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

The federal inventory lists 49 bridges in Corson County: 19 rated good, 26 fair, and 4 poor.

4 of the 49 bridges in Corson County, South Dakota, are rated in poor condition (8.2%) in the 2025 National Bridge Inventory, as of August 20, 2026.
19 bridges (38.8%) are rated good and 26 (53.1%) fair.
The median Corson County bridge was built in 1973.
The busiest poor-rated bridge is Irr US012 over Claymore Ck (built 1958), carrying about 1,378 vehicles a day.

Good 38.8% · Fair 53.1% · Poor 8.2% of 49 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.

Bridge	Built	Vehicles/day	Condition
Irr US012 over Claymore Ck	1958	1,378	Poor
104TH Street over Hump Creek	1930	30	Poor
Township Road over Dirt Lodge Creek	1932	30	Poor
Corson County 35 over Grand River	1990	20	Poor

Busiest bridges in the county

Bridge	Built	Vehicles/day	Condition
Irr US012 over Claymore Ck	1958	1,378	Poor
Irr US012 over Deep Bank Ck	1965	1,091	Fair
Irr US012 over Br Snake Ck	1965	1,091	Fair
Irr US012 over Snake Ck	1966	1,091	Fair
Irr SD020 over Ck	2000	956	Good
Irr SD063 over Oak Ck	1980	864	Fair
Irr SD063 over Ck	1980	864	Good
Irr SD1806 over Burlington Northern RR	1973	826	Fair
Irr SD1806 over Oahe Lk (grand Rv)	1963	826	Fair
Irr US012 over Ck	1964	636	Fair

Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.

All of South Dakota: South Dakota 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.