Total bridges
102
Public highway bridges in Blaine County
County profile · official public datasets
Blaine County, MT
102 public highway bridges tracked in the FHWA National Bridge Inventory: 33.3% rated Good, 56.9% Fair, 9.8% Poor.
- 102
- Public bridges
- 33.3%
- Good condition
- 9.8%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Blaine County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.
- 44th
- of 56 on Poor share
- 9.8%
- Poor-condition share
- 102
- public highway bridges
- 1969
- 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.
Blaine County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Blaine County ranks #44 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.8%). Blaine County, Montana contains 102 public highway bridges. Roughly 33.3% are rated “Good,” 56.9% “Fair,” and 9.8% “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
33.3%
34 of 102 rated 7-9
Fair condition
56.9%
58 of 102 rated 5-6
Poor condition
9.8%
10 of 102 rated 4 or below
In-state Poor-share rank
#44 of 56
Among Montana counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 102 NBI-tracked bridges by lowest applicable component rating.
Good 33.3% (34)
Fair 56.9% (58)
Poor 9.8% (10)
Blaine County's Poor-condition bridges carry 12,603 vehicle crossings a day
That is 18.9% of the county's reported daily bridge traffic on 9.8% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 1,260 crossings a day against 687 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.
Computed over the 102 of 102 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
59.8% of Blaine County's bridges have passed the 50-year mark
61 of the 102 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 33.3% 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.
One structure carries 25.4% of the county's Poor-condition bridge traffic
IRR - US 2 over MILK RIVER, built 1964, carries 3,196 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 10-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 12,603 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Blaine County's bridges were built
102 bridges with a recorded construction year, grouped by decade
- 1910s 1
1910–1919
1 bridges
- 1920s 2
1920–1929
2 bridges
- 1930s
1930–1939
16 bridges
- 1940s
1940–1949
20 bridges
- 1950s
1950–1959
13 bridges
- 1960s 6
1960–1969
6 bridges
- 1970s 5
1970–1979
5 bridges
- 1980s 4
1980–1989
4 bridges
- 1990s
1990–1999
9 bridges
- 2000s
2000–2009
9 bridges
- 2010s
2010–2019
13 bridges
- 2020s 4
2020–2029
4 bridges
What this shows Construction peaked in the 1940s, when 20 of the county's bridges still in the inventory were built, which is 19.6% of those with a recorded year. That cohort is now 75 to 84 years old in the 2024 inventory. Its average build year is 1969, 8 years older than the Montana average of 1977.
How Blaine County compares with Montana's closest counties by inventory size
The 5 Montana counties nearest Blaine County in number of bridges, with their condition splits. Its 9.8% Poor share is the 3rd-lowest of these 6. Its average build year of 1969 against a peer-group mean of 1978 is 9 years older.
Showing the 5 closest of 55 Montana counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Valley County | 104 | 10.6% | 76.9% | 12.5% | 1975 |
| Blaine County (this page) | 102 | 33.3% | 56.9% | 9.8% | 1969 |
| Phillips County | 101 | 13.9% | 69.3% | 16.8% | 1972 |
| Madison County | 97 | 32% | 56.7% | 11.3% | 1981 |
| Richland County | 97 | 28.9% | 68% | 3.1% | 1988 |
| Pondera County | 96 | 51% | 44.8% | 4.2% | 1975 |
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 Blaine 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 Blaine County, both outside Montana so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside MT (102 bridges here).
- La Plata County, CO · 102 bridges
- Clarke County, GA · 102 bridges
- Pulaski County, IN · 102 bridges
- Clark County, KS · 102 bridges
Similar average build year
Nearest mean year-built outside MT (1969 here).
- Cook County, IL · avg 1969 · 1,721 bridges
- Fresno County, CA · avg 1969 · 916 bridges
- Cuyahoga County, OH · avg 1969 · 871 bridges
- Ventura County, CA · avg 1969 · 501 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Poor-condition bridges (10)
REDROCK RD
PoorOver: FORT BELKNAP CANAL 008
3M NW CHINOOK, Blaine, MT
Built 1933 Load: 8.2 t ADT: 211
MIDDLE RD
PoorOver: BATTLE CREEK 056
4M N CHINOOK, Blaine, MT
Built 1920 Load: 13.2 t ADT: 100
EKEGREN RD
PoorOver: THIRTY MILE CREEK 097
3M E HARLEM, Blaine, MT
Built 1938 Load: 19.0 t ADT: 100
S 529-CLEAR CR RD
PoorOver: MILK RIVER
1M W CHINOOK, Blaine, MT
Built 1967 Load: 19.1 t ADT: 254
US 2
PoorOver: LODGE CREEK
CHINOOK, Blaine, MT
Built 1942 Load: 23.6 t ADT: 2,254
US 2
PoorOver: IRRIGATION-STOCKPASS
1M E CHINOOK, Blaine, MT
Built 1940 Load: 23.6 t ADT: 2,254
US 2
PoorOver: DRAINAGE
ZURICH, Blaine, MT
Built 1940 Load: 28.1 t ADT: 2,067
LODGE CREEK RD
PoorOver: FORT BELKNAP CANAL
1M NE CHINOOK, Blaine, MT
Built 1952 Load: 28.1 t ADT: 100
US 2
PoorOver: DRAINAGE
4M E CHINOOK, Blaine, MT
Built 1940 Load: 31.8 t ADT: 2,067
IRR - US 2
PoorOver: MILK RIVER
FORT BELKNAP AGENCY, Blaine, MT
Built 1964 Load: 33.6 t ADT: 3,196
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.