County profile · official public datasets

Gallatin County, MT

210 public highway bridges tracked in the FHWA National Bridge Inventory: 19% rated Good, 76.7% Fair, 4.3% Poor.

210
Public bridges: 19%
Good condition: 4.3%
Poor condition

The verdict

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

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

Top 30%
lowest Poor share in state: 4.3%
Poor-condition share: 210
public highway bridges: 1977
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.

Gallatin County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Gallatin County ranks #17 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 4.3%). Gallatin County, Montana contains 210 public highway bridges. Roughly 19% are rated “Good,” 76.7% “Fair,” and 4.3% “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

210

Public highway bridges in Gallatin County

Good condition

19%

40 of 210 rated 7-9

Fair condition

76.7%

161 of 210 rated 5-6

Poor condition

4.3%

9 of 210 rated 4 or below

In-state Poor-share rank

#17 of 56

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

Condition distribution

Share of 210 NBI-tracked bridges by lowest applicable component rating.

Good

19% (40)

Fair

76.7% (161)

Poor

4.3% (9)

Gallatin County's Poor-condition bridges carry 14,725 vehicle crossings a day

That is 1.8% of the county's reported daily bridge traffic on 4.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,636 crossings a day against 2,342 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 210 of 210 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

53.8% of Gallatin County's bridges have passed the 50-year mark

113 of the 210 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 19% 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 57.5% of the county's Poor-condition bridge traffic

I 90 over ABANDONED RR, built 1969, carries 8,465 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 9-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 14,725 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

3
1910s

1
1920s

7
1930s

4
1940s

7
1950s

25
1960s

54
1970s

21
1980s

20
1990s

14
2000s

20
2010s

30
2020s

4

What this shows Construction peaked in the 1960s, when 54 of the county's bridges still in the inventory were built, which is 25.7% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1977) matches the Montana average (1977).

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

The 5 Montana counties nearest Gallatin County in number of bridges, with their condition splits. Its 4.3% Poor share is the 1st-lowest of these 6. Its average build year of 1977 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 Gallatin 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 (this page)	210	19%	76.7%	4.3%	1977
Missoula County	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 Gallatin 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 Gallatin County, both outside Montana so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside MT (210 bridges here).

Fulton County, IL · 210 bridges
Clinton County, IN · 210 bridges
Howard County, IA · 210 bridges
Montgomery County, IA · 210 bridges

Similar average build year

Nearest mean year-built outside MT (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

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

All 210 Good 40 Fair 161 Poor 9

All bridges (210)

Sort:

Gallatin County Bridge Snapshot

Condition distribution

Gallatin County's Poor-condition bridges carry 14,725 vehicle crossings a day

53.8% of Gallatin County's bridges have passed the 50-year mark

One structure carries 57.5% of the county's Poor-condition bridge traffic

How Gallatin 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 (210)

RIVER RD

OLD TOWN RD

N 7TH AVE-FRTG RD

DEER CREEK TRLHD.

WILLIAMS BR RD

DRY CR SCHOOL RD

KELLY CANYON RD

DURNAM ROAD

STORM CASTLE ROAD

HAMILTON RD

MONFORTON SCH RD

HEEB RD

CAMP CREEK RD

S 205-FRONTAGE RD

BIGGS HAUGLAND RD

STAGECOACH TRL RD

AMSTERDAM RD

SPAULDING BR RD

GRAYLING CR RD

I 90

SIXTEEN MILE ROAD

PINE BUTTE RD

LITTLE BEAR RD

PORCUPINE CR ROAD

LANGOHR ROAD

MANHATTAN S RD

COBB HILL RD

16 MILE CREEK RD

PINE BUTTE RD

US 191

US 191 FH 42

I 90

MAIDEN ROCK RD

MOFFIT GULCH RD

US 287

KELLY CANYON RD

LONE MOUNTAIN TRL

US 191-HUFFINE LN

FRONTAGE RD-S 205

DRY CREEK RD

STORM CASTLE ROAD

LAW RD

OLD YELLOWSTONE TR

W DRY CREEK RD

AMSTERDAM RD

SPIRE ROCK CG LOOP

SPIRE ROCK CG LOOP

I 90

US 191 FH 42

FRONTAGE RD-S 205

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