Bridge conditions in Sioux County, North Dakota

22 inventoried bridges · 1 rated poor · 2025 National Bridge Inventory

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

Sioux County tracks close to typical: 1 of its 22 inventoried bridges (4.5%) are rated poor, against a national rate of about 7%.

1 of the 22 bridges in Sioux County, North Dakota, are rated in poor condition (4.5%) in the 2025 National Bridge Inventory, as of August 20, 2026.
12 bridges (54.5%) are rated good and 9 (40.9%) fair.
The median Sioux County bridge was built in 1965.
The busiest poor-rated bridge is Irr Bia Rte 29 over One Mile Creek (built 1950), carrying about 401 vehicles a day.

Good 54.5% · Fair 40.9% · Poor 4.5% of 22 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 Bia Rte 29 over One Mile Creek	1950	401	Poor

Busiest bridges in the county

Bridge	Built	Vehicles/day	Condition
Irrsr Nd Hiway 24 over Beaver Holes Creek	1965	1,830	Fair
Irrsr Nd Hiway 24 over Porcupine Creek	1963	1,740	Fair
Irrsr Nd Hiway 24 over Battle Creek	1965	1,700	Fair
Irr Bia Rte 3 over Four Mile Creek Bridge	2010	1,000	Good
Irrsr Nd Hiway 24 over Four Mile Creek	1930	750	Fair
Irr Bia Rte 29 over One Mile Creek	1950	401	Poor
Irrsr Nd Highway 6 over Porcupine Creek	1987	270	Fair
Irrsr Nd Highway 6 over Creek	1948	250	Good
Irrsr Nd Highway 6 over Creek	1987	250	Good
Irrsr Nd Highway 6 over Creek	1949	250	Good

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

All of North Dakota: North 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.