Bridge conditions in Sully County, South Dakota

31 inventoried bridges · 6 rated poor · 2025 National Bridge Inventory

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

Of the 31 Sully County bridges in the federal inventory, 6 carry a poor rating. That 19.4% share is roughly 3x the national average.

6 of the 31 bridges in Sully County, South Dakota, are rated in poor condition (19.4%) in the 2025 National Bridge Inventory, as of August 20, 2026.
14 bridges (45.2%) are rated good and 11 (35.5%) fair.
The median Sully County bridge was built in 1974.
The busiest poor-rated bridge is 188 Street over Ck (built 1964), carrying about 75 vehicles a day.

Good 45.2% · Fair 35.5% · Poor 19.4% of 31 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
188 Street over Ck	1964	75	Poor
315 Avenue over Medicine Ck	1956	64	Poor
320 Avenue over Ck	1961	25	Poor
301 Avenue over Okobojo Creek	1961	20	Poor
302 Avenue over Okobojo Ck	1962	20	Poor
195 Street over Medicine Knoll Ck	1913	10	Poor

Busiest bridges in the county

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
176 Street over Okobojo Ck	2023	230	Good
196 St over Cow Ck	2006	180	Good
185 Street over Medicine Ck	2021	150	Good
185 Street over Medicine Knoll Ck	1930	150	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.