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Bridge conditions in Gregory County, South Dakota

51 inventoried bridges · 5 rated poor · 2025 National Bridge Inventory

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

The federal inventory lists 51 bridges in Gregory County: 15 rated good, 31 fair, and 5 poor.

5 of the 51 bridges in Gregory County, South Dakota, are rated in poor condition (9.8%) in the 2025 National Bridge Inventory, as of August 20, 2026.
15 bridges (29.4%) are rated good and 31 (60.8%) fair.
The median Gregory County bridge was built in 1977.
The busiest poor-rated bridge is 354 Avenue over Ponca Ck (built 1952), carrying about 189 vehicles a day.

Good 29.4% · Fair 60.8% · Poor 9.8% of 51 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
354 Avenue over Ponca Ck	1952	189	Poor
State Park Rd over South Scalp Ck	1963	50	Poor
352 Avenue over Willow Ck	1956	36	Poor
366 Avenue over North Scalp Ck	2015	36	Poor
297 Street over Ck	1920	10	Poor

Busiest bridges in the county

Bridge	Built	Vehicles/day	Condition
345 Avenue over South Fork Whetstone Ck	2001	560	Good
SD047 over Ck	1957	552	Fair
SD047 over Ck	1957	552	Fair
SD044 over Bull Ck	1971	540	Good
SD044 over Lone Tree Ck	1971	540	Fair
SD044 over Dixon Ck	1971	540	Fair
SD044 over Ck	1971	540	Fair
SD044 over Ck	1964	504	Good
SD251 over Ponca Ck	1984	400	Good
SD251 over Masdon Ck	1996	400	Good

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.