County profile · official public datasets

Lake County, MT

117 public highway bridges tracked in the FHWA National Bridge Inventory: 57.3% rated Good, 27.4% Fair, 15.4% Poor.

117
Public bridges
57.3%
Good condition
15.4%
Poor condition

The verdict

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

Lake County pairs a higher-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

52nd
of 56 on Poor share
15.4%
Poor-condition share
117
public highway bridges
1995
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.

Lake County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Lake County ranks #52 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 15.4%). Lake County, Montana contains 117 public highway bridges. Roughly 57.3% are rated “Good,” 27.4% “Fair,” and 15.4% “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

117

Public highway bridges in Lake County

Good condition

57.3%

67 of 117 rated 7-9

Fair condition

27.4%

32 of 117 rated 5-6

Poor condition

15.4%

18 of 117 rated 4 or below

In-state Poor-share rank

#52 of 56

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

Condition distribution

Share of 117 NBI-tracked bridges by lowest applicable component rating.

Good
57.3% (67)
Fair
27.4% (32)
Poor
15.4% (18)

Lake County's Poor-condition bridges carry 12,161 vehicle crossings a day

That is 5% of the county's reported daily bridge traffic on 15.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 676 crossings a day against 2,502 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 117 of 117 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

17.9% of Lake County's bridges have passed the 50-year mark

21 of the 117 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 57.3% 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 58.2% of the county's Poor-condition bridge traffic

IRR - US 93 over NINE PIPE RESERVOIR, built 1933, carries 7,072 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 18-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 12,161 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Lake County's bridges were built

117 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 2000s, when 39 of the county's bridges still in the inventory were built, which is 33.3% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1995, 18 years newer than the Montana average of 1977.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

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

The 5 Montana counties nearest Lake County in number of bridges, with their condition splits. Its 15.4% Poor share is the 6th-lowest of these 6. Its average build year of 1995 against a peer-group mean of 1976 is 19 years newer.

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

Bridge inventory size and condition shares for Lake County and the 5 Montana counties closest to it in inventory size
County Bridges Poor
Park County 124 10.5%
Sanders County 120 7.5%
Lake County (this page) 117 15.4%
Rosebud County 114 5.3%
Powell County 113 6.2%
Dawson County 109 6.4%

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

Similar inventory size

Nearest county inventories outside MT (117 bridges here).

Similar average build year

Nearest mean year-built outside MT (1995 here).

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

All 117 Good 67 Fair 32 Poor 18

Good-condition bridges (67)

US 93

Good

Over: WILDLIFE CROSSING

2 MILES NORTH OF RONAN, Lake, MT

Built 2007 ADT: 10,600

Foothill Road

Good

Over: Mission Res Inlet 043

6 M SE St ignatius, Lake, MT

Built 2023 ADT: 100

MOLLMAN PASS TRAIL

Good

Over: N KICKING HORSE RES 009

4M S RONAN, Lake, MT

Built 2023 ADT: 100

HILLSIDE ROAD

Good

Over: POST CREEK

7 M SOUTH RONAN, Lake, MT

Built 2023 ADT: 100

GARCON GULCH ROAD

Good

Over: LITTLE BITTERROOT RIVER

7 M N HOT SPRINGS, Lake, MT

Built 2022 Load: 13.6 t ADT: 100

SKYLINE DR

Good

Over: PABLO 3A CANAL 039

3M S POLSON, Lake, MT

Built 2015 Load: 14.5 t ADT: 100

OLD FREIGHT ROAD

Good

Over: MISSION CREEK 105

2M NW ST IGNATIUS, Lake, MT

Built 2012 Load: 14.9 t ADT: 100

MCDONALD LAKE RD

Good

Over: POST CREEK 078

6M N ST IGNATIUS, Lake, MT

Built 2015 Load: 15.4 t ADT: 100

NO DATA ENTERED

Good

Over: ARCHIBALD CR

NO DATA ENTERED, Lake, MT

Built 2004 Load: 19.8 t ADT: 50

SKYLINE DR

Good

Over: PABLO FEEDER CANAL 040

2M SE POLSON, Lake, MT

Built 2011 Load: 19.9 t ADT: 100

LEIGHTON RD

Good

Over: PABLO CANAL 37A

2M NW PABLO, Lake, MT

Built 2018 Load: 20.0 t ADT: 100

OLD FREIGHT RD

Good

Over: POST CREEK 053

3M NW ST IGNATIUS, Lake, MT

Built 2016 Load: 20.0 t ADT: 100

FORD RD

Good

Over: PABLO FEEDER CANAL 072

3M SE POLSON, Lake, MT

Built 2017 Load: 20.0 t ADT: 100

JOCKO CANYON RD

Good

Over: JOCKO RIVER 013

9M E ARLEE, Lake, MT

Built 1930 Load: 21.4 t ADT: 100

NFSR

Good

Over: PONY CREEK

CONDON AREA, Lake, MT

Built 2008 Load: 21.7 t ADT: 40

BUFFALO BRIDGE RD

Good

Over: FLATHEAD RIVER 084

10M W POLSON, Lake, MT

Built 1993 Load: 21.8 t ADT: 100

SKYLINE DR

Good

Over: PABLO 3A CANAL 038

4M S POLSON, Lake, MT

Built 2013 Load: 21.8 t ADT: 100

TIMBERLANE RD

Good

Over: N CROW CREEK 002

3M SE RONAN, Lake, MT

Built 2017 Load: 22.7 t ADT: 100

NFSR

Good

Over: CAT CREEK

CONDON AREA, Lake, MT

Built 2008 Load: 22.7 t ADT: 40

IRR BIA RTE 1114

Good

Over: JOCKO RIVER

14.5 KM EAST OF ARLEE, Lake, MT

Built 1996 Load: 24.5 t ADT: 75

EAST POST CREEK RD

Good

Over: POST CREEK 080

5 MI N OF ST IGNATIUS, Lake, MT

Built 2022 Load: 24.5 t ADT: 100

CANYON MILL RD

Good

Over: PABLO FEEDER CANAL 008

2M NW RONAN, Lake, MT

Built 2014 Load: 24.5 t ADT: 100

SALMON PRAIRIE RD

Good

Over: SWAN RIVER 091

22M S SWAN LAKE, Lake, MT

Built 1986 Load: 24.5 t ADT: 100

HILLSIDE ROAD

Good

Over: MISSION CREEK

1.5 MILES E. ST. IGNATIUS, Lake, MT

Built 2021 Load: 25.4 t ADT: 100

FOREST ROAD

Good

Over: CREEK

NORTH FORK LOST CREEK, Lake, MT

Built 2005 Load: 25.9 t ADT: 30

MISSION DAM ROAD

Good

Over: MISSION CREEK

2M E ST IGNATIUS, Lake, MT

Built 2021 Load: 26.3 t ADT: 100

FOREST ROAD

Good

Over: CEDAR CREEK

FATTY-PIPER CONNECTOR, Lake, MT

Built 1985 Load: 26.6 t ADT: 10

KERR DAM RD

Good

Over: IRRIGATION CANAL

2M SW POLSON, Lake, MT

Built 1995 Load: 27.2 t ADT: 2,099

FOREST ROAD

Good

Over: DOG CREEK

NO DATA ENTERED, Lake, MT

Built 2013 Load: 28.2 t ADT: 40

FOREST ROAD

Good

Over: NORTH FORK LOST CREEK

NORTH LOST, Lake, MT

Built 2015 Load: 28.2 t ADT: 40

SYSTEM ROAD

Good

Over: FATTY CREEK

FATTY PIPER CONNECTOR, Lake, MT

Built 2013 Load: 28.8 t ADT: 40

FOREST ROAD

Good

Over: JIM CREEK

PECK LAKE ROAD, Lake, MT

Built 2016 Load: 29.2 t ADT: 50

FOREST ROAD

Good

Over: PIPER CREEK

PIPER CREEK ROAD, Lake, MT

Built 2015 Load: 29.5 t ADT: 40

STASSO ROAD

Good

Over: PABLO CANAL 37A4

5 MILES SOUTH OF POLSON, Lake, MT

Built 2020 Load: 29.9 t ADT: 100

FOREST ROAD

Good

Over: NORTH FORK LOST CREEK

SOUTH LOST, Lake, MT

Built 2014 Load: 30.1 t ADT: 40

STREAM

Good

Over: SOUTH MISSION RESERVIOR

6 MILES EAST ST IGNATIUS, Lake, MT

Built 2019 Load: 30.8 t ADT: 100

IRR BIA RTE 12

Good

Over: MISSION DAM CREEK

3.2KM E OF ST IGNATIUS MT, Lake, MT

Built 2010 Load: 32.7 t ADT: 30

KAISER RD

Good

Over: PABLO CANAL 031

6M W RONAN, Lake, MT

Built 2014 Load: 32.7 t ADT: 100

MINESINGER TRAIL

Good

Over: PABLO FEEDER CANAL 003

6M SE POLSON, Lake, MT

Built 1978 Load: 32.7 t ADT: 100

COURVILLE TRAIL

Good

Over: PABLO FEEDER CANAL 006

7M SW POLSON, Lake, MT

Built 1978 Load: 32.7 t ADT: 100

US 93

Good

Over: WILDLIFE CROSSING

2M NE RONAN, Lake, MT

Built 2007 Load: 32.7 t ADT: 10,600

US 93

Good

Over: AGRICULTURAL CROSSING

2M N RONAN, Lake, MT

Built 2007 Load: 32.7 t ADT: 10,600

IRR - US 93

Good

Over: PABLO FEEDER CANAL

2M SE POLSON, Lake, MT

Built 2006 Load: 32.7 t ADT: 15,561

N RESEVOIR RD

Good

Over: PABLO FEEDER CANAL 085

5M S POLSON, Lake, MT

Built 2009 Load: 34.5 t ADT: 857

US 93

Good

Over: SABINE CREEK-WILDLIFE

1M S ST IGNATIUS, Lake, MT

Built 2006 Load: 35.4 t ADT: 6,822

LIL BITTERROOT RD

Good

Over: LITTLE BITTERROOT R 063

7M E HOT SPRINGS, Lake, MT

Built 2013 Load: 36.3 t ADT: 100

IRR - US 93

Good

Over: JOCKO RIVER

ARLEE, Lake, MT

Built 2005 Load: 36.3 t ADT: 8,330

S VALLEY CREEK RD

Good

Over: JOCKO RIVER 056

4M NW ARLEE, Lake, MT

Built 2012 Load: 37.2 t ADT: 122

FOREST SYSTEM ROAD

Good

Over: SWAN RIVER

NO DATA ENTERED, Lake, MT

Built 2012 Load: 37.3 t ADT: 50

US 93

Good

Over: WILDLIFE UNDERPASS

1M SE POLSON, Lake, MT

Built 2006 Load: 38.1 t ADT: 7,781

Read our methodology - how this data is sourced, computed, and verified.

Related

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Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges

Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.