County profile · official public datasets

Prairie County, MT

46 public highway bridges tracked in the FHWA National Bridge Inventory: 13% rated Good, 80.4% Fair, 6.5% Poor.

46
Public bridges: 13%
Good condition: 6.5%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Prairie 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.

34th
of 56 on Poor share: 6.5%
Poor-condition share: 46
public highway bridges: 1962
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.

Prairie County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Prairie County ranks #34 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.5%). Prairie County, Montana contains 46 public highway bridges. Roughly 13% are rated “Good,” 80.4% “Fair,” and 6.5% “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

Public highway bridges in Prairie County

Good condition

13%

6 of 46 rated 7-9

Fair condition

80.4%

37 of 46 rated 5-6

Poor condition

6.5%

3 of 46 rated 4 or below

In-state Poor-share rank

#34 of 56

Among Montana counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 46 NBI-tracked bridges by lowest applicable component rating.

Good

13% (6)

Fair

80.4% (37)

Poor

6.5% (3)

Prairie County's Poor-condition bridges carry 214 vehicle crossings a day

That is 0.5% of the county's reported daily bridge traffic on 6.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 71 crossings a day against 397 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 46 of 46 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

73.9% of Prairie County's bridges have passed the 50-year mark

34 of the 46 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 13% 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 37.4% of the county's Poor-condition bridge traffic

CB ROUTE RD over BR MAIN CANAL 035, built 1928, carries 80 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 3-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 214 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1920s

1
1930s

10
1940s

6
1950s

1
1960s

7
1970s

14
1980s

2
2000s

2
2010s

1
2020s

1

What this shows Construction peaked in the 1970s, when 14 of the county's bridges still in the inventory were built, which is 30.4% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1962, 15 years older than the Montana average of 1977.

How Prairie County compares with Montana's closest counties by inventory size

The 5 Montana counties nearest Prairie County in number of bridges, with their condition splits. Its 6.5% Poor share is the 3rd-lowest of these 6. Its average build year of 1962 against a peer-group mean of 1979 is 17 years older.

Showing the 5 closest of 55 Montana counties eligible for comparison.

Bridge inventory size and condition shares for Prairie County and the 5 Montana counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Judith Basin County	48	56.3%	31.3%	12.5%	1979
Hill County	46	58.7%	34.8%	6.5%	1983
Prairie County (this page)	46	13%	80.4%	6.5%	1962
McCone County	44	11.4%	79.5%	9.1%	1967
Chouteau County	42	54.8%	38.1%	7.1%	1981
Carter County	41	31.7%	63.4%	4.9%	1985

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 Prairie 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 Prairie County, both outside Montana so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside MT (46 bridges here).

Butts County, GA · 46 bridges
Marion County, GA · 46 bridges
Towns County, GA · 46 bridges
Russell County, KY · 46 bridges

Similar average build year

Nearest mean year-built outside MT (1962 here).

Berks County, PA · avg 1962 · 667 bridges
Pecos County, TX · avg 1962 · 470 bridges
Bristol County, MA · avg 1962 · 384 bridges
Norfolk County, MA · avg 1962 · 343 bridges

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

All 46 Good 6 Fair 37 Poor 3

All bridges (46)

Sort:

Prairie County Bridge Snapshot

Condition distribution

Prairie County's Poor-condition bridges carry 214 vehicle crossings a day

73.9% of Prairie County's bridges have passed the 50-year mark

One structure carries 37.4% of the county's Poor-condition bridge traffic

How Prairie County compares with Montana's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (46)

SPRING CREEK RD

COUNTY ROAD 119

S 253

OLD HWY 10 W

OLD HWY 10 E

OLD HWY 10 E

FRONTAGE ROAD 114

FRONTAGE ROAD 168

I 94

I 94

I 94

S 340

I 94

S 253

S 253

OLD HWY 10 W

CB ROUTE RD

S 253

S 253

S 253

I 94

I 94

OLD HWY 10 W

I 94

I 94

TEN MILE RD

I 94

I 94

OLD HWY 10 W

CB ROUTE RD

CONNS COULEE RD

I 94

I 94

I 94

S 253

TEN MILE RD

I 94

FALLON TOWER RD

WHITNEY CREEK RD

CABIN CREEK RD

I 94

S 340

CABIN CREEK RD

CB ROUTE RD

MILWAUKEE RD

CB ROUTE RD

Related