South Dakota Bridge Infrastructure: A Complete Analysis

South Dakota is home to 5,883 bridges spanning 66 counties, making it one of the most significant bridge inventories in the country. These bridges carry a combined 8,253,701 vehicle crossings every day. Here is a comprehensive look at the state of South Dakota's bridge infrastructure based on the latest National Bridge Inventory data.

South Dakota earns an overall infrastructure grade of F based on the percentage of its bridges in poor condition. Currently, 945 bridges (16.1%) are rated poor, compared to the national average of 6.7%. The average bridge in South Dakota is 50 years old, older than the national average of 48 years.

Of the state's 5,883 bridges, 2,038 are in good condition, 2,900 are fair, and 945 are poor. View the full breakdown on the [South Dakota report card](/reports/south-dakota).

These are the bridges carrying the highest daily traffic volumes across South Dakota. High-traffic bridges are critical infrastructure -- their condition directly affects the commutes of tens of thousands of drivers.

The following bridges have the lowest sufficiency ratings in South Dakota. These structures are the most likely candidates for federal repair or replacement funding under the Bipartisan Infrastructure Law.

South Dakota's oldest bridges tell the story of the state's transportation history. Some of these structures have been in continuous service for over a century.

South Dakota's bridge infrastructure grade of F reflects both the current condition of the state's bridges and the scale of the challenge ahead. With an average bridge age of 50 years, many of these structures are approaching or past the 50-75 year design life typical of most bridges. The state's ability to maintain and replace aging bridges will determine whether conditions improve or deteriorate in the coming decade.

For county-by-county breakdowns, historical trends, and individual bridge profiles, visit the [South Dakota state page](/bridges/south-dakota) or the [South Dakota report card](/reports/south-dakota). You can also explore how South Dakota compares to other states in our [state rankings](/blog/best-bridge-infrastructure-by-state-2025).