When the Roads Washed Away
In March 2019, rapid snowmelt and heavy rainfall caused catastrophic flooding across the Pine Ridge and Rosebud reservations in southwestern South Dakota. Approximately 8,000 people lost water supplies. Seven communities on Pine Ridge lost water service entirely. Floodwaters hampered or trapped roughly 2,000 people, and horseback riders were dispatched to reach isolated communities after roads washed out. (SDPB News; NPR)
Hidden Timber Dam broke in Todd County on the Rosebud Reservation, compounding the damage. Road infrastructure that was already marginal failed under conditions that, while severe, were not unprecedented for the region. With limited alternative routes and vast distances between communities, the loss of roads and crossings did not create detours. It created isolation. (SDPB News)
South Dakota ranks #3 nationally for bridges in poor condition. (ARTBA 2025) The conditions that made Pine Ridge so vulnerable in 2019 exist at varying degrees across the state's county bridge network.
Scale of the Problem
South Dakota has 5,883 bridges. (ARTBA 2025) Of those, 945 are rated in poor condition, a rate of 16%. Only Iowa (19%) and West Virginia (18%) rank higher. The national average is 6.7%. (ARTBA 2025)
The state's inventory is much smaller than Iowa's 23,716 bridges, but the percentage is nearly as bad. South Dakota's bridge count is comparable to smaller states, yet its poor rate sits in the top three. (ARTBA 2025)
Beyond the 945 poor bridges, ARTBA estimates that 2,192 bridges statewide need some form of repair work. The estimated cost to address the full backlog is $1.555 billion, split across replacement ($912 million), rehabilitation ($281 million), and other structural work ($279 million). (ARTBA 2025)
The full state profile is available on ARTBA's South Dakota bridge report.
Who Owns What
The ranking is not a statewide failure. It is a county-level problem. SDDOT maintains 1,822 bridges, and only 36 of them are rated poor, a 2% poor rate. (FHWA NBI 2024) The state highway system is in strong shape.
Counties own 3,658 bridges, which is 62% of the statewide inventory. Of those, 869 are rated poor, a 24% poor rate. Counties account for 92% of all poor bridges in South Dakota. (FHWA NBI 2024)
| Owner | Bridges | Poor | % Poor |
|---|---|---|---|
| SDDOT | 1,822 | 36 | 2% |
| Counties | 3,658 | 869 | 24% |
| Cities | 183 | 17 | 9% |
| Federal/Tribal | 132 | 17 | 13% |
Iowa's problem is fragmented local ownership. West Virginia's problem is concentrated state ownership. South Dakota resembles Iowa: 92% of poor bridges belong to counties. Sixty-six county governments maintain the bulk of the inventory, each working with different budgets, different equipment, and different levels of engineering capacity.
The 132 federal and tribal bridges in the NBI likely understate the true tribal bridge count. The NBI classifies bridges by owner, not by location. Many bridges on reservation land are county-owned or state-owned and appear in those categories instead. (FHWA NBI 2024)
A State Split by a River
The Missouri River runs north to south through the center of South Dakota, dividing the state into two distinct regions. East of the river is agricultural flatland with higher population density, older bridge inventories, and a dense grid of county roads built to move crops to market. West of the river is sparsely populated rangeland, home to tribal reservations and the Black Hills, with fewer bridges but far greater distances between them. (SDDOT)
South Dakota covers 77,116 square miles with a population of approximately 910,000, roughly 11.3 people per square mile. The state maintains about 1 bridge for every 13 square miles of land and 6.5 bridges per 1,000 residents. Six highway crossings span the Missouri River itself, each inspected annually by the state. (SDDOT; FHWA NBI 2024)
Nearly every county with the worst bridge conditions is east of the river. West River counties like Harding (49 bridges, 1 poor) and Perkins (60 bridges, 3 poor) have low bridge counts and low poor counts. The density of the problem is in the east, where the agricultural road grid created thousands of small crossings over creeks and drainage channels, many of them built 50 to 70 years ago. (FHWA NBI 2024)
West of the river, the problem is different. Bridges are fewer, but losing one can cut off access across enormous distances. The 2019 Pine Ridge flooding demonstrated what that looks like in practice.
Where the Problem Is Worst
Eight counties account for a disproportionate share of the state's poor bridges. All eight are East River agricultural counties. (FHWA NBI 2024)
| County | Total | Poor | % Poor | Region |
|---|---|---|---|---|
| Spink | 176 | 53 | 30% | East River |
| Brookings | 232 | 53 | 23% | East River |
| Union | 169 | 41 | 24% | East River |
| Beadle | 150 | 40 | 27% | East River |
| Hand | 126 | 40 | 32% | East River |
| Roberts | 155 | 39 | 25% | East River |
| Grant | 205 | 38 | 19% | East River |
| Turner | 143 | 38 | 27% | East River |
Minnehaha County, home to Sioux Falls, has the most total bridges in the state at 394. Only 36 are rated poor, a 9% rate, which reflects the urban county's larger tax base and maintenance capacity. (FHWA NBI 2024)
The highest-traffic deficient bridge statewide is on US 12 over Moccasin Creek in Brown County near Aberdeen. Built in 1954, it carries 21,635 vehicles per day. (FHWA NBI 2024)
What Poor Bridges Cost Farmers and Communities
South Dakota has 933 weight-posted bridges and 71 fully closed bridges. Combined, 1,004 bridges are restricted or closed, which is 17% of the entire inventory. Of the posted bridges, 637 are in poor condition. (FHWA NBI 2024)
Agriculture is the dominant industry, and the county bridge network is the farm-to-market supply chain. Modern farm equipment often exceeds 20 tons loaded. Many posted bridges carry 3-to-10-ton limits. A farmer with a posted bridge on the direct route to a grain elevator faces a choice between an illegal overweight crossing and a detour that may add 10 or 20 miles to every trip. (SDDOT)
Driving on roads needing repair costs each South Dakota driver approximately $562 per year in additional vehicle operating costs. (ASCE) Those costs come from accelerated depreciation, increased repairs, fuel consumption, and tire wear.
Emergency response is the secondary concern. Volunteer fire departments and rural ambulance services cover vast distances at 11.3 people per square mile. Bridge closures lengthen response routes, and weight restrictions can exclude heavy apparatus entirely. Nationally, 76% of BIA and tribal roads are unimproved earth and gravel, which compounds the access problem on reservation land. (BIA; ASCE)
Funding and the Slow Grind
South Dakota has made real investments. In 2015, the legislature passed SB 1 with bipartisan support (55-11 in the House), raising the gas tax from 22 to 28 cents per gallon. The bill created the Bridge Improvement Grant (BIG) program, which provides $15 million per year for county bridge projects. The state also established the Rural Access Infrastructure Fund (RAIF), distributing $31 million in grant funding for small bridges and culverts. (SD Legislature; SDDOT)
Federal IIJA money added $225 million through the Bridge Formula Program over FY2022-2026. As of June 2025, $180 million was accessible and $65.9 million had been committed to 62 projects. (ARTBA; FHWA) That $225 million covers roughly 14% of the $1.555 billion backlog.
The gas tax has held at 28 cents per gallon for 11 years with no inflation indexing. Purchasing power has declined steadily over that period. (SD Legislature)
| Year | Poor Bridges | % Poor |
|---|---|---|
| 2015 | 1,066 | 18% |
| 2019 | 991 | 17% |
| 2021 | 1,018 | 17% |
| 2025 | 945 | 16% |
Over 10 years, South Dakota reduced its poor bridge count by 121 and its poor rate by 2 percentage points. Progress is real but slow against a $1.555 billion backlog. (ARTBA 2025)
SDDOT Secretary Joel Jundt has publicly stated that bridge and road conditions are expected to worsen over the next decade. (South Dakota Searchlight)
Tribal Bridges and the Data Gap
South Dakota has nine federally recognized reservations. The National Bridge Inventory lists 132 federal and tribal bridges statewide, with 17 rated poor (13%). (FHWA NBI 2024)
That 132 figure likely understates the true count. The NBI classifies bridges by owner, not by geographic location. Many bridges on reservation land are county-owned or state-owned and appear under those agencies in the data. County-level numbers for reservation counties illustrate the gap: Oglala Lakota County shows 17 bridges with 0 poor, and Todd County shows 13 bridges with 1 poor. Those figures reflect the data classification system, not necessarily the condition of infrastructure on the ground. (FHWA NBI 2024)
Nationally, the federal Tribal Transportation Facility Bridge Program received $825 million over five years under the IIJA. (FHWA) How much of that reaches South Dakota's nine reservations depends on application cycles, tribal capacity, and the federal allocation process.
The 2019 Pine Ridge flooding, described at the top of this page, is the clearest illustration of what these data gaps mean in practice. When the available data says a county has 17 bridges and 0 are poor, but a single flood event can strand 2,000 people and cut water service to seven communities, the published numbers represent a floor for the scope of the problem on reservation land, not a ceiling. (SDPB News; NPR)
What "Poor Condition" Means
A bridge is classified as being in "poor condition" if any one of its three primary components (deck, superstructure, or substructure) receives a rating of 4 or below on the NBI's 0-to-9 scale. A poor rating does not mean a bridge is unsafe or at risk of collapse. It means the bridge has deteriorated to the point where it needs repair or replacement. Bridges rated poor are typically subject to increased inspection frequency, load restrictions, or both.
Data Sources
Statewide totals (5,883 bridges, 945 poor, 16%, rank #3) are from the ARTBA 2025 Bridge Report, based on 2025 FHWA National Bridge Inventory data. Ownership breakdowns, county-level data, and posting/closure figures are from the FHWA NBI 2024 dataset. Funding data is from SDDOT, the South Dakota Legislature, ARTBA, and FHWA as cited inline. The 2019 flooding account is based on reporting by SDPB News and NPR.
Caveats
Bridge inspection practices and rating standards can vary by inspector and agency. The NBI captures a snapshot in time; individual bridge conditions change between inspection cycles. The 132 federal/tribal bridge count likely understates the true scope of tribal bridge infrastructure because the NBI classifies bridges by owner, not by location. County-level data for reservation counties reflects this classification gap. Percentages are rounded to whole numbers except for the national average (6.7%), which is ARTBA's published figure.