County profile · official public datasets

Petersburg County, AK

141 public highway bridges tracked in the FHWA National Bridge Inventory: 44.7% rated Good, 47.5% Fair, 7.8% Poor.

141
Public bridges: 44.7%
Good condition: 7.8%
Poor condition

The verdict

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

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

18th
of 27 on Poor share: 7.8%
Poor-condition share: 141
public highway bridges: 1992
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.

Petersburg County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Petersburg County ranks #18 of 27 Alaska counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.8%). Petersburg County, Alaska contains 141 public highway bridges. Roughly 44.7% are rated “Good,” 47.5% “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

141

Public highway bridges in Petersburg County

Good condition

44.7%

63 of 141 rated 7-9

Fair condition

47.5%

67 of 141 rated 5-6

Poor condition

7.8%

11 of 141 rated 4 or below

In-state Poor-share rank

#18 of 27

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

Condition distribution

Share of 141 NBI-tracked bridges by lowest applicable component rating.

Good

44.7% (63)

Fair

47.5% (67)

Poor

7.8% (11)

Petersburg County's Poor-condition bridges carry 50 vehicle crossings a day

That is 0.5% of the county's reported daily bridge traffic on 7.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 6 crossings a day against 87 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 105 of 141 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

5% of Petersburg County's bridges have passed the 50-year mark

7 of the 141 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 44.7% 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 20% of the county's Poor-condition bridge traffic

KAKE ACCESS - USFS over MUSKEG CREEK, built 1981, carries 10 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 11-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 50 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1940s

1
1960s

3
1970s

16
1980s

42
1990s

34
2000s

38
2010s

6
2020s

1

What this shows Construction peaked in the 1980s, when 42 of the county's bridges still in the inventory were built, which is 29.8% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1992) matches the Alaska average (1989).

How Petersburg County compares with Alaska's closest counties by inventory size

The 5 Alaska counties nearest Petersburg 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 1992 against a peer-group mean of 1991 is in line with the group.

Showing the 5 closest of 26 Alaska counties eligible for comparison.

Bridge inventory size and condition shares for Petersburg County and the 5 Alaska counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Petersburg County (this page)	141	44.7%	47.5%	7.8%	1992
Anchorage County	134	49.3%	50%	0.7%	1992
Hoonah-Angoon County	125	49.6%	35.2%	15.2%	1994
Matanuska-Susitna County	120	50.8%	43.3%	5.8%	1993
Fairbanks North Star County	111	50.5%	42.3%	7.2%	1988
Kenai Peninsula County	103	35.9%	50.5%	13.6%	1988

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

Similar inventory size

Nearest county inventories outside AK (141 bridges here).

St. Johns County, FL · 141 bridges
Renville County, MN · 141 bridges
Warren County, NY · 141 bridges
Geauga County, OH · 141 bridges

Similar average build year

Nearest mean year-built outside AK (1992 here).

Johnson County, KS · avg 1992 · 781 bridges
Wake County, NC · avg 1992 · 760 bridges
Benton County, AR · avg 1992 · 410 bridges
Nodaway County, MO · avg 1992 · 396 bridges

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

All 141 Good 63 Fair 67 Poor 11

Fair-condition bridges (67)

Sort:

Petersburg County Bridge Snapshot

Condition distribution

Petersburg County's Poor-condition bridges carry 50 vehicle crossings a day

5% of Petersburg County's bridges have passed the 50-year mark

One structure carries 20% of the county's Poor-condition bridge traffic

How Petersburg County compares with Alaska'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 (67)

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MITKOF HIGHWAY

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MARINE HWY ROUTE

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43500

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