County profile · official public datasets

Mercer County, PA

438 public highway bridges tracked in the FHWA National Bridge Inventory: 39.3% rated Good, 45.2% Fair, 15.5% Poor.

438
Public bridges: 39.3%
Good condition: 15.5%
Poor condition

The verdict

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

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

51st
of 67 on Poor share: 15.5%
Poor-condition share: 438
public highway bridges: 1972
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.

Mercer County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Mercer County ranks #51 of 67 Pennsylvania counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 15.5%). Mercer County, Pennsylvania contains 438 public highway bridges. Roughly 39.3% are rated “Good,” 45.2% “Fair,” and 15.5% “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

438

Public highway bridges in Mercer County

Good condition

39.3%

172 of 438 rated 7-9

Fair condition

45.2%

198 of 438 rated 5-6

Poor condition

15.5%

68 of 438 rated 4 or below

In-state Poor-share rank

#51 of 67

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

Condition distribution

Share of 438 NBI-tracked bridges by lowest applicable component rating.

Good

39.3% (172)

Fair

45.2% (198)

Poor

15.5% (68)

Mercer County's Poor-condition bridges carry 67,582 vehicle crossings a day

That is 5.7% of the county's reported daily bridge traffic on 15.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,009 crossings a day against 2,263 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 437 of 438 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

59.6% of Mercer County's bridges have passed the 50-year mark

261 of the 438 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 39.3% 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 14.5% of the county's Poor-condition bridge traffic

SR 58 MAIN STREET over OVER WOLF CREEK, built 1967, carries 9,802 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 68-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 67,582 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

5
1900s

7
1910s

7
1920s

14
1930s

19
1940s

7
1950s

40
1960s

147
1970s

34
1980s

46
1990s

42
2000s

27
2010s

40
2020s

3

What this shows Construction peaked in the 1960s, when 147 of the county's bridges still in the inventory were built, which is 33.6% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1972) matches the Pennsylvania average (1970).

How Mercer County compares with Pennsylvania's closest counties by inventory size

The 5 Pennsylvania counties nearest Mercer County in number of bridges, with their condition splits. Its 15.5% Poor share is the 5th-lowest of these 6. Its average build year of 1972 against a peer-group mean of 1973 is in line with the group.

Showing the 5 closest of 66 Pennsylvania counties eligible for comparison.

Bridge inventory size and condition shares for Mercer County and the 5 Pennsylvania counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Somerset County	454	33%	52.6%	14.3%	1969
Dauphin County	449	22%	69.5%	8.5%	1972
Erie County	442	37.8%	52.7%	9.5%	1976
Mercer County (this page)	438	39.3%	45.2%	15.5%	1972
Tioga County	429	49.4%	47.3%	3.3%	1977
Fayette County	422	39.6%	42.7%	17.8%	1971

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

Similar inventory size

Nearest county inventories outside PA (438 bridges here).

Licking County, OH · 439 bridges
Butte County, CA · 437 bridges
Clay County, MO · 436 bridges
Pinellas County, FL · 435 bridges

Similar average build year

Nearest mean year-built outside PA (1972 here).

Santa Clara County, CA · avg 1972 · 964 bridges
Madison County, AL · avg 1972 · 710 bridges
Kern County, CA · avg 1972 · 668 bridges
Middlesex County, NJ · avg 1972 · 563 bridges

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

All 438 Good 172 Fair 198 Poor 68

Good-condition bridges (172)

Sort:

Mercer County Bridge Snapshot

Condition distribution

Mercer County's Poor-condition bridges carry 67,582 vehicle crossings a day

59.6% of Mercer County's bridges have passed the 50-year mark

One structure carries 14.5% of the county's Poor-condition bridge traffic

How Mercer County compares with Pennsylvania's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (172)

BR 1704

SR 1101 CREEK ROAD

SR 258 BUTLER PIKE

BRIDGE 499 T-907

SR 518 WALNUT ST

SR 208 GROVE CITY

SR 158 Mercer Rd.

SR 60 BROADWAY AVE

BRIDGE 2809 T-955

SR 173 Grove City

BRIDGE 2012 T-704

BRIDGE 1112 T-695

SR 208 NORTH ST.

SR 62 EXPRESSWAY

SR 4024 BAKER HILL

SR 19

SR 18 COLLEGE AVE.

SR 58 WILSON AVE.

SR 4006 PORTER RD

WILLIAMSON ROAD

SR 58 MERCER ROAD

BRIDGE 2633 T-698

BRIDGE 109 T-865

BUTLER PIKE

SR 4021 Atlantic

BRIDGE 1416 T-634

SR 173 GROVE CITY

SR 62 MAIN STREET

SR 80 EB

SR 80 WB

SR 846 RIVER ROAD

BRIDGE 612 T-884

BRIDGE 1915 T-549

BRIDGE 1003 T-668

SR 518 LONGVIEW RD

SR 4017 WARNER RD

SR 18 MAIN STREET

SR 3018 BUCKEYE DR

BRIDGE 2629 T-944

BRIDGE 2709 T-912

BUTLER PIKE

KINSMEN ROAD

SR 846 ORNGVLLE.RD

SR 258 LAKE ROAD

SR 80 EB

SR 80 WB

BRIDGE 1917 T-496

SR 58 S.DIAMOND ST

BRIDGE 2630 T-403

BRIDGE 607 T-846

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