County profile · official public datasets

Missoula County, MT

206 public highway bridges tracked in the FHWA National Bridge Inventory: 33.5% rated Good, 58.7% Fair, 7.8% Poor.

206
Public bridges: 33.5%
Good condition: 7.8%
Poor condition

The verdict

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

Missoula County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

39th
of 56 on Poor share: 7.8%
Poor-condition share: 206
public highway bridges: 1976
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.

Missoula County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Missoula County ranks #39 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.8%). Missoula County, Montana contains 206 public highway bridges. Roughly 33.5% are rated “Good,” 58.7% “Fair,” and 7.8% “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.

Total bridges

206

Public highway bridges in Missoula County

Good condition

33.5%

69 of 206 rated 7-9

Fair condition

58.7%

121 of 206 rated 5-6

Poor condition

7.8%

16 of 206 rated 4 or below

In-state Poor-share rank

#39 of 56

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

Condition distribution

Share of 206 NBI-tracked bridges by lowest applicable component rating.

Good

33.5% (69)

Fair

58.7% (121)

Poor

7.8% (16)

Missoula County's Poor-condition bridges carry 32,823 vehicle crossings a day

That is 3.7% of the county's reported daily bridge traffic on 7.8% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,051 crossings a day against 3,889 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 206 of 206 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

55.8% of Missoula County's bridges have passed the 50-year mark

115 of the 206 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 33.5% 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 40.4% of the county's Poor-condition bridge traffic

I 90 over INT RESERVE STREET, built 1966, carries 13,266 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 16-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 32,823 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1920s

2
1930s

4
1940s

7
1950s

14
1960s

63
1970s

41
1980s

21
1990s

13
2000s

23
2010s

13
2020s

4

What this shows Construction peaked in the 1960s, when 63 of the county's bridges still in the inventory were built, which is 30.6% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1976) matches the Montana average (1977).

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

The 5 Montana counties nearest Missoula County in number of bridges, with their condition splits. Its 7.8% Poor share is the 4th-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1979 is in line with the group.

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

Bridge inventory size and condition shares for Missoula County and the 5 Montana counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Beaverhead County	226	23.9%	66.8%	9.3%	1978
Gallatin County	210	19%	76.7%	4.3%	1977
Missoula County (this page)	206	33.5%	58.7%	7.8%	1976
Flathead County	204	30.9%	64.2%	4.9%	1983
Lewis and Clark County	200	58%	36.5%	5.5%	1979
Lincoln County	190	38.4%	46.8%	14.7%	1977

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

Similar inventory size

Nearest county inventories outside MT (206 bridges here).

Dale County, AL · 206 bridges
Henry County, IN · 206 bridges
Audubon County, IA · 206 bridges
Bourbon County, KS · 206 bridges

Similar average build year

Nearest mean year-built outside MT (1976 here).

Marion County, IN · avg 1976 · 958 bridges
Mohave County, AZ · avg 1976 · 641 bridges
Comanche County, OK · avg 1976 · 593 bridges
Prince George's County, MD · avg 1976 · 576 bridges

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

All 206 Good 69 Fair 121 Poor 16

Fair-condition bridges (121)

Sort:

Missoula County Bridge Snapshot

Condition distribution

Missoula County's Poor-condition bridges carry 32,823 vehicle crossings a day

55.8% of Missoula County's bridges have passed the 50-year mark

One structure carries 40.4% of the county's Poor-condition bridge traffic

How Missoula 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

Fair-condition bridges (121)

W.SIDE 9-MILE RD

RATTLESNAKE CR RD

MATTIE V

I 90

I 90

I 90

US 12 FH 11

S 263

I 90

I 90

I 90

I 90 WB

I 90

W NINEMILE RD

GOLD CR RD

I 90

I 90

I 90

SCHWARTZ CREEK RD

SCOTT ST

MORMON PK RD

I 90

PLACID LAKE RD S

GLACIER CREEK RD

US 12-E BROADWAY S

N RESERVE ST

I 90

I 90

I 90

I 90

I 90

I 90

W NINEMILE RD

PLACID LAKE RD

SAWMILL GULCH RD

PINERIDGE RD

PINERIDGE RD

GUEST RANCH RD

MALLARD WAY

EXPRESSWAY RD

INTERNATIONAL DR

I 90 EB

ELK FLATS RD

EXPO PKWY

I 90 WB

S 200

MULLAN RD

SPOOK LAKE RD

0427: MCNAMARA ROA

I 90

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