County profile · official public datasets

Deer Lodge County, MT

68 public highway bridges tracked in the FHWA National Bridge Inventory: 27.9% rated Good, 66.2% Fair, 5.9% Poor.

68
Public bridges: 27.9%
Good condition: 5.9%
Poor condition

The verdict

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

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

29th
of 56 on Poor share: 5.9%
Poor-condition share: 68
public highway bridges: 1973
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.

Deer Lodge County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Deer Lodge County ranks #29 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5.9%). Deer Lodge County, Montana contains 68 public highway bridges. Roughly 27.9% are rated “Good,” 66.2% “Fair,” and 5.9% “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 Deer Lodge County

Good condition

27.9%

19 of 68 rated 7-9

Fair condition

66.2%

45 of 68 rated 5-6

Poor condition

5.9%

4 of 68 rated 4 or below

In-state Poor-share rank

#29 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

27.9% (19)

Fair

66.2% (45)

Poor

5.9% (4)

Deer Lodge County's Poor-condition bridges carry 270 vehicle crossings a day

That is 0.3% of the county's reported daily bridge traffic on 5.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 68 crossings a day against 1,283 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.

48.5% of Deer Lodge County's bridges have passed the 50-year mark

33 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 27.9% 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% of the county's Poor-condition bridge traffic

COUNTY ROAD 098 over CLARK FORK RIVER 020, built 1920, 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 4-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 270 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

1
1930s

7
1940s

3
1950s

3
1960s

13
1970s

18
1980s

5
1990s

4
2000s

3
2010s

10

What this shows Construction peaked in the 1970s, when 18 of the county's bridges still in the inventory were built, which is 26.5% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1973) matches the Montana average (1977).

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

The 5 Montana counties nearest Deer Lodge County in number of bridges, with their condition splits. Its 5.9% Poor share is the 5th-lowest of these 6. Its average build year of 1973 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 Deer Lodge 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
Silver Bow County	68	16.2%	82.4%	1.5%	1974
Deer Lodge County (this page)	68	27.9%	66.2%	5.9%	1973
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 Deer Lodge 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 Deer Lodge 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 (1973 here).

Jefferson County, AL · avg 1973 · 1,068 bridges
Erie County, NY · avg 1973 · 906 bridges
Davidson County, TN · avg 1973 · 832 bridges
Lancaster County, PA · avg 1973 · 801 bridges

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

All 68 Good 19 Fair 45 Poor 4

Fair-condition bridges (45)

Sort:

Deer Lodge County Bridge Snapshot

Condition distribution

Deer Lodge County's Poor-condition bridges carry 270 vehicle crossings a day

48.5% of Deer Lodge County's bridges have passed the 50-year mark

One structure carries 37% of the county's Poor-condition bridge traffic

How Deer Lodge 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 (45)

BRIDGE LN

MAPLE STREET

SYCAMORE STREET

S 569

S 569

NO DATA ENTERED

S 1

S 1

S 43

NO DATA ENTERED

STEWART ST

S 1 FH 17

FRONTAGE ROAD 146

S 1

NO DATA ENTERED

S 48

I 90

I 90

I 90

FRONTAGE ROAD 146

FRONTAGE ROAD 146

I 90

I 90

FRONTAGE ROAD 011

S 1

S 1

CRACKERVILLE RD

STEWART ST

I 90

S 1

FRONTAGE ROAD 137

I 90

S 273

NORTH CABLE RD

W RIVER RD

I 90

ROAD 169

NO DATA ENTERED

GALEN RD E

NO DATA ENTERED

CEDAR STREET

ROAD

S 43

S 43

NO DATA ENTERED

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