Total bridges
43
Public highway bridges in Slope County
County profile · official public datasets
Slope County, ND
43 public highway bridges tracked in the FHWA National Bridge Inventory: 86% rated Good, 14% Fair, 0% Poor.
- 43
- Public bridges
- 86%
- Good condition
- 0%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Slope County pairs a top-5% lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 4%
- lowest Poor share in state
- 0%
- Poor-condition share
- 43
- public highway bridges
- 1989
- avg year built
Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.
Slope County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Slope County ranks #2 of 53 North Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 0%). Slope County, North Dakota contains 43 public highway bridges. Roughly 86% are rated “Good,” 14% “Fair,” and 0% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.
Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.
Source: FHWA National Bridge Inventory. See methodology for full definitions.
Good condition
86%
37 of 43 rated 7-9
Fair condition
14%
6 of 43 rated 5-6
Poor condition
0%
0 of 43 rated 4 or below
In-state Poor-share rank
#2 of 53
Among North Dakota counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 43 NBI-tracked bridges by lowest applicable component rating.
Good 86% (37)
Fair 14% (6)
Poor 0% (0)
16.3% of Slope County's bridges have passed the 50-year mark
7 of the 43 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 86% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.
Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.
When Slope County's bridges were built
43 bridges with a recorded construction year, grouped by decade
- 1930s 2
1930–1939
2 bridges
- 1950s 4
1950–1959
4 bridges
- 1960s 1
1960–1969
1 bridges
- 1970s 2
1970–1979
2 bridges
- 1980s
1980–1989
13 bridges
- 1990s
1990–1999
8 bridges
- 2000s 3
2000–2009
3 bridges
- 2010s
2010–2019
6 bridges
- 2020s 4
2020–2029
4 bridges
What this shows Construction peaked in the 1980s, when 13 of the county's bridges still in the inventory were built, which is 30.2% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1989, 14 years newer than the North Dakota average of 1975.
How Slope County compares with North Dakota's closest counties by inventory size
The 5 North Dakota counties nearest Slope County in number of bridges, with their condition splits. Its 0% Poor share is the 2nd-lowest of these 6. Its average build year of 1989 against a peer-group mean of 1982 is 7 years newer.
Showing the 5 closest of 52 North Dakota counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Ramsey County | 48 | 43.8% | 47.9% | 8.3% | 1987 |
| Adams County | 45 | 35.6% | 51.1% | 13.3% | 1972 |
| Dickey County | 43 | 62.8% | 37.2% | 0% | 1986 |
| Slope County (this page) | 43 | 86% | 14% | 0% | 1989 |
| Wells County | 41 | 61% | 31.7% | 7.3% | 1980 |
| Benson County | 40 | 57.5% | 25% | 17.5% | 1983 |
Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Slope County's. Source: FHWA National Bridge Inventory, 2024 release.
Nationwide counties with similar inventory size or average build year
Two NBI-derived peer sets for Slope County, both outside North Dakota so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside ND (43 bridges here).
- Franklin County, FL · 43 bridges
- Calhoun County, GA · 43 bridges
- Roscommon County, MI · 43 bridges
- Weston County, WY · 43 bridges
Similar average build year
Nearest mean year-built outside ND (1989 here).
- Harris County, TX · avg 1989 · 4,029 bridges
- Mecklenburg County, NC · avg 1989 · 746 bridges
- Buffalo County, NE · avg 1989 · 459 bridges
- Brazos County, TX · avg 1989 · 370 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Fair-condition bridges (6)
145TH AVE SW
FairOver: CREEK
6 SOUTH 3 WEST OF AMIDON, Slope, ND
Built 1933 Load: 10.1 t ADT: 10
58TH ST SW
FairOver: DEEP CREEK
11 WEST 7 NORTH OF AMIDON, Slope, ND
Built 1979 Load: 19.1 t ADT: 26
172ND AVE SW
FairOver: BEAVER CREEK
SW OUTSKIRTS OF MARMARTH, Slope, ND
Built 1955 Load: 19.2 t ADT: 200
US HIGHWAY 12
FairOver: LITTLE MISSOURI RIVER
AT MARMARTH, Slope, ND
Built 1950 Load: 37.7 t ADT: 580
US HIGHWAY 12
FairOver: BRANCH OF BEAVER CREEK
3 WEST OF MARMARTH, Slope, ND
Built 1950 Load: 52.4 t ADT: 510
COUNTY HIGHWAY
FairOver: TRIB OF CANNONBALL RIVER
4 NORTH 19 EAST AMIDON, Slope, ND
Built 2000 Load: 57.8 t ADT: 100
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.