County profile · official public datasets

Silver Bow County, MT

68 public highway bridges tracked in the FHWA National Bridge Inventory: 16.2% rated Good, 82.4% Fair, 1.5% Poor.

68
Public bridges: 16.2%
Good condition: 1.5%
Poor condition

The verdict

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

Silver Bow County posts a top-quartile lowest Poor-condition share among rated counties in the state across rated county bridge inventory.

Top 11%
lowest Poor share in state: 1.5%
Poor-condition share: 68
public highway bridges: 1974
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.

Silver Bow County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Silver Bow County ranks #6 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 1.5%). Silver Bow County, Montana contains 68 public highway bridges. Roughly 16.2% are rated “Good,” 82.4% “Fair,” and 1.5% “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 Silver Bow County

Good condition

16.2%

11 of 68 rated 7-9

Fair condition

82.4%

56 of 68 rated 5-6

Poor condition

1.5%

1 of 68 rated 4 or below

In-state Poor-share rank

#6 of 56

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

Condition distribution

Share of 68 NBI-tracked bridges by lowest applicable component rating.

Good

16.2% (11)

Fair

82.4% (56)

Poor

1.5% (1)

Silver Bow County's Poor-condition bridges carry 100 vehicle crossings a day

That is 0% of the county's reported daily bridge traffic on 1.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 100 crossings a day against 4,292 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 68 of 68 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

60.3% of Silver Bow County's bridges have passed the 50-year mark

41 of the 68 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 16.2% 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 100% of the county's Poor-condition bridge traffic

GERMAN GULCH RD over INT VICTOR I 15 003, built 1961, carries 100 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 1-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 100 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1930s

1
1950s

7
1960s

30
1970s

13
1980s

4
2000s

4
2010s

8

What this shows Construction peaked in the 1960s, when 30 of the county's bridges still in the inventory were built, which is 44.1% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1974) matches the Montana average (1977).

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

The 5 Montana counties nearest Silver Bow County in number of bridges, with their condition splits. Its 1.5% Poor share is the 2nd-lowest of these 6. Its average build year of 1974 against a peer-group mean of 1975 is in line with the group.

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

Bridge inventory size and condition shares for Silver Bow County and the 5 Montana counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Granite County	73	37%	52.1%	11%	1974
Custer County	71	14.1%	84.5%	1.4%	1969
Glacier County	71	38%	56.3%	5.6%	1978
Deer Lodge County	68	27.9%	66.2%	5.9%	1973
Silver Bow County (this page)	68	16.2%	82.4%	1.5%	1974
Sheridan County	66	16.7%	80.3%	3%	1979

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

Similar inventory size

Nearest county inventories outside MT (68 bridges here).

Bent County, CO · 68 bridges
Columbia County, GA · 68 bridges
Talbot County, GA · 68 bridges
Wilcox County, GA · 68 bridges

Similar average build year

Nearest mean year-built outside MT (1974 here).

Knox County, TN · avg 1974 · 588 bridges
Summit County, OH · avg 1974 · 563 bridges
Onondaga County, NY · avg 1974 · 472 bridges
Orange County, NY · avg 1974 · 472 bridges

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

All 68 Good 11 Fair 56 Poor 1

All bridges (68)

Sort:

Silver Bow County Bridge Snapshot

Condition distribution

Silver Bow County's Poor-condition bridges carry 100 vehicle crossings a day

60.3% of Silver Bow County's bridges have passed the 50-year mark

One structure carries 100% of the county's Poor-condition bridge traffic

How Silver Bow 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 (68)

SHIELDS AVE

PUMPHOUSE RD

FAIRMONT RD

PALMER ST

I 15

I 15

I 90

I 90

I 15

DIVIDE CREEK RD

I 15

MT HIGHLAND DR

18131: MAIDEN ROCK

I 115S

N MONTANA ST

I 15

I 15

CENTENNIAL AVE

I 15

I 15

S 43

I 115S

I 115S

MILES CROSSING

I 90

S 41

BURLINGTON ST

TRAPPER CREEK RD

I 15

I 15

LEXINGTON AVE

OREGON AVE

CONTINENTAL DR

S 43

I 90

I 90

SHERIDAN AVE

I 15

I 15

I 15

I 90

SILVER BOW RD

S ROCKER RD

FAIRMONT RD

SHIELDS AVE

I 15

I 15

NO DATA ENTERED

I 15

S MONTANA ST

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