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.

Total bridges

43

Public highway bridges in Slope County

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

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.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

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.

Bridge inventory size and condition shares for Slope County and the 5 North Dakota counties closest to it in inventory size
County Bridges Poor
Ramsey County 48 8.3%
Adams County 45 13.3%
Dickey County 43 0%
Slope County (this page) 43 0%
Wells County 41 7.3%
Benson County 40 17.5%

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).

Similar average build year

Nearest mean year-built outside ND (1989 here).

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 43 Good 37 Fair 6 Poor 0

All bridges (43)

145TH AVE SW

Fair

Over: CREEK

6 SOUTH 3 WEST OF AMIDON, Slope, ND

Built 1933 Load: 10.1 t ADT: 10

58TH ST SW

Fair

Over: DEEP CREEK

11 WEST 7 NORTH OF AMIDON, Slope, ND

Built 1979 Load: 19.1 t ADT: 26

172ND AVE SW

Fair

Over: BEAVER CREEK

SW OUTSKIRTS OF MARMARTH, Slope, ND

Built 1955 Load: 19.2 t ADT: 200

US HIGHWAY 12

Fair

Over: LITTLE MISSOURI RIVER

AT MARMARTH, Slope, ND

Built 1950 Load: 37.7 t ADT: 580

US HIGHWAY 12

Fair

Over: BRANCH OF BEAVER CREEK

3 WEST OF MARMARTH, Slope, ND

Built 1950 Load: 52.4 t ADT: 510

COUNTY HIGHWAY

Fair

Over: TRIB OF CANNONBALL RIVER

4 NORTH 19 EAST AMIDON, Slope, ND

Built 2000 Load: 57.8 t ADT: 100

70TH ST SW

Good

Over: N FORK CEDAR CREEK

6 SOUTH 8 EAST OF AMIDON, Slope, ND

Built 1977 Load: 19.1 t ADT: 25

US HIGHWAY 85

Good

Over: PHILBRICK CREEK

4 NORTH OF JCT. ND 21, Slope, ND

Built 1937 Load: 19.1 t ADT: 920

US HIGHWAY 67

Good

Over: NORTH FORK CEDAR CREEK

11 SOUTH JCT ND 21, Slope, ND

Built 1952 Load: 21.0 t ADT: 180

128TH AVE SW

Good

Over: N. FORK CEDAR CREEK

10 SOUTH 14 EAST AMIDON, Slope, ND

Built 1990 Load: 22.9 t ADT: 50

128TH AVE SW

Good

Over: N. FORK CANNONBALL RIVER

6 NORTH 13 EAST OF AMIDON, Slope, ND

Built 1983 Load: 23.8 t ADT: 26

71ST ST SW

Good

Over: CHANTA PETA CREEK

7 SOUTH 18 EAST OF AMIDON, Slope, ND

Built 1985 Load: 23.8 t ADT: 50

64TH ST SW

Good

Over: DEEP CREEK

10 WEST OF AMIDON, Slope, ND

Built 1984 Load: 24.5 t ADT: 60

126TH AVE SW

Good

Over: CANNONBALL RIVER

7 NORTH 16 EAST OF AMIDON, Slope, ND

Built 1991 Load: 26.1 t ADT: 65

76TH ST SW

Good

Over: NORTH FORK CEDAR CREEK

11 SOUTH 15 EAST AMIDON, Slope, ND

Built 1988 Load: 27.0 t ADT: 50

US HIGHWAY 85

Good

Over: BRANCH-CANNONBALL RIVER

2 SOUTH OF JCT. ND 21, Slope, ND

Built 1963 Load: 29.2 t ADT: 1,010

132ND AVE SW

Good

Over: N. FORK CANNONBALL RIVER

4 NORTH 10 EAST OF AMIDON, Slope, ND

Built 1998 Load: 31.3 t ADT: 24

154TH AVE SW

Good

Over: WEST FORK DEEP CREEK

2 NORTH 17 EAST MARMARTH, Slope, ND

Built 1985 Load: 32.7 t ADT: 20

COUNTY HIGHWAY

Good

Over: CREEK

10 WEST OF AMIDON, Slope, ND

Built 1984 Load: 32.7 t ADT: 60

76TH STREET SW

Good

Over: DEEP CREEK

8 N 2.5 W OF BOWMAN, Slope, ND

Built 1987 Load: 32.7 t ADT: 50

EAST RIVER ROAD

Good

Over: FIRST CREEK

6 NORTH 6 WEST AMIDON, Slope, ND

Built 1985 Load: 32.7 t ADT: 35

COUNTY HIGHWAY

Good

Over: SAND CREEK

6 WEST OF AMIDON, Slope, ND

Built 1983 Load: 32.7 t ADT: 60

54TH ST SW

Good

Over: PHILBRICK CREEK

7 NORTH 14 EAST OF AMIDON, Slope, ND

Built 1986 Load: 32.7 t ADT: 100

130TH AVE SW

Good

Over: NORTH FORK CEDAR CREEK

11 SOUTH 12 EAST AMIDON, Slope, ND

Built 1993 Load: 33.6 t ADT: 50

US HIGHWAY 12

Good

Over: BNRR SEPARATION

1 WEST OF MARMARTH, Slope, ND

Built 1984 Load: 35.9 t ADT: 561

FOREST HIGHWAY

Good

Over: LITTLE MISSOURI RIVER

22 WEST 5 NORTH OF AMIDON, Slope, ND

Built 2002 Load: 38.8 t ADT: 20

ND HIGHWAY 21

Good

Over: CREEK

1 WEST JCT ND 67, Slope, ND

Built 2021 Load: 38.9 t ADT: 507

US HIGHWAY 12

Good

Over: LITTLE BEAVER CREEK

1 WEST OF MARMARTH, Slope, ND

Built 1987 Load: 40.5 t ADT: 520

EAST RIVER ROAD

Good

Over: SAND CREEK

9 WEST 8 NORTH OF AMIDON, Slope, ND

Built 2016 Load: 40.8 t ADT: 25

149TH AVE. SW

Good

Over: DEEP CREEK

12 NORTH 22 EAST MARMARTH, Slope, ND

Built 1993 Load: 40.8 t ADT: 45

COUNTY HIGHWAY

Good

Over: N FORK CANNONBALL RIVER

7 EAST OF AMIDON, Slope, ND

Built 1992 Load: 40.8 t ADT: 24

COUNTY HIGHWAY

Good

Over: N. FORK CEDAR CREEK

8 SOUTH 12 EAST AMIDON, Slope, ND

Built 2016 Load: 40.8 t ADT: 26

COUNTY HIGHWAY

Good

Over: N. FORK CEDAR CREEK

9 SOUTH 12 EAST OF AMIDON, Slope, ND

Built 1995 Load: 40.8 t ADT: 35

COUNTY HIGHWAY

Good

Over: CHANTA PETA CREEK

5 SOUTH 16 EAST OF AMIDON, Slope, ND

Built 2016 Load: 40.8 t ADT: 26

ND HIGHWAY 21

Good

Over: CREEK

4 EAST OF JCT US 85, Slope, ND

Built 2021 Load: 41.6 t ADT: 440

COUNTY HIGHWAY

Good

Over: CANNONBALL CREEK

11 N 3 W OF MARMARTH, Slope, ND

Built 2012 Load: 42.1 t ADT: 100

COUNTY HIGHWAY

Good

Over: CREEK

1 NORTHEAST OF MARMARTH, Slope, ND

Built 2016 Load: 42.1 t ADT: 45

US HIGHWAY 85

Good

Over: CREEK

12 NORTH OF US 12, Slope, ND

Built 1991 Load: 45.6 t ADT: 1,080

ND HIGHWAY 21

Good

Over: CANNONBALL RIVER

3 EAST JCT US 85, Slope, ND

Built 1983 Load: 58.2 t ADT: 350

COUNTY HIGHWAY

Good

Over: TRIB OF CANNONBALL RIVER

4 NORTH 16 EAST AMIDON, Slope, ND

Built 2000 Load: 59.7 t ADT: 100

Old highway 16

Good

Over: CREEK

11.5 N 3 W OF MARMARTH, Slope, ND

Built 2010 Load: 62.1 t ADT: 100

ND HIGHWAY 21

Good

Over: CREEK

6 EAST OF JCT. NO 67, Slope, ND

Built 2021 Load: 99.9 t ADT: 507

ND HIGHWAY 21

Good

Over: CREEK

8 EAST JCT ND 67, Slope, ND

Built 2021 Load: 99.9 t ADT: 507

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.