County profile · official public datasets

Ionia County, MI

119 public highway bridges tracked in the FHWA National Bridge Inventory: 32.8% rated Good, 58.8% Fair, 8.4% Poor.

119
Public bridges: 32.8%
Good condition: 8.4%
Poor condition

The verdict

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

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

Top 41%
lowest Poor share in state: 8.4%
Poor-condition share: 119
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.

Ionia County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Ionia County ranks #34 of 83 Michigan counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 8.4%). Ionia County, Michigan contains 119 public highway bridges. Roughly 32.8% are rated “Good,” 58.8% “Fair,” and 8.4% “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

119

Public highway bridges in Ionia County

Good condition

32.8%

39 of 119 rated 7-9

Fair condition

58.8%

70 of 119 rated 5-6

Poor condition

8.4%

10 of 119 rated 4 or below

In-state Poor-share rank

#34 of 83

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

Condition distribution

Share of 119 NBI-tracked bridges by lowest applicable component rating.

Good

32.8% (39)

Fair

58.8% (70)

Poor

8.4% (10)

Ionia County's Poor-condition bridges carry 7,750 vehicle crossings a day

That is 1.6% of the county's reported daily bridge traffic on 8.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 775 crossings a day against 2,513 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 119 of 119 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

47.1% of Ionia County's bridges have passed the 50-year mark

56 of the 119 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 32.8% 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 32.7% of the county's Poor-condition bridge traffic

M-21 over MAPLE RIVER, built 1929, carries 2,533 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 10-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 7,750 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

2
1920s

10
1930s

5
1940s

2
1950s

26
1960s

4
1970s

13
1980s

19
1990s

12
2000s

12
2010s

12
2020s

2

What this shows Construction peaked in the 1950s, when 26 of the county's bridges still in the inventory were built, which is 21.8% of those with a recorded year. That cohort is now 65 to 74 years old in the 2024 inventory. Its average build year (1974) matches the Michigan average (1976).

How Ionia County compares with Michigan's closest counties by inventory size

The 5 Michigan counties nearest Ionia County in number of bridges, with their condition splits. Its 8.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1974 against a peer-group mean of 1976 is in line with the group.

Showing the 5 closest of 82 Michigan counties eligible for comparison.

Bridge inventory size and condition shares for Ionia County and the 5 Michigan counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
St. Joseph County	132	28.8%	59.1%	12.1%	1979
Van Buren County	129	32.6%	60.5%	7%	1976
Montcalm County	121	37.2%	57.9%	5%	1977
Ionia County (this page)	119	32.8%	58.8%	8.4%	1974
Branch County	118	24.6%	54.2%	21.2%	1973
Chippewa County	112	22.3%	65.2%	12.5%	1974

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

Similar inventory size

Nearest county inventories outside MI (119 bridges here).

Carroll County, AR · 119 bridges
Grant County, AR · 119 bridges
Stafford County, KS · 119 bridges
Grayson County, KY · 119 bridges

Similar average build year

Nearest mean year-built outside MI (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 119 Good 39 Fair 70 Poor 10

All bridges (119)

Sort:

Ionia County Bridge Snapshot

Condition distribution

Ionia County's Poor-condition bridges carry 7,750 vehicle crossings a day

47.1% of Ionia County's bridges have passed the 50-year mark

One structure carries 32.7% of the county's Poor-condition bridge traffic

How Ionia County compares with Michigan'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 (119)

DILDINE ROAD

PECK LAKE ROAD

BRIDGE STREET

GOLD LAKE ROAD

KNOX RD

ROBERTS ROAD

HUBBARDSTON ROAD

BONANZA ROAD

MAPLE ROAD

KEEFER RD

DAVID HWY

MUSGROVE HWY

TUPPER LAKE ROAD

PRAIRIE CREEK ROAD

CLINTON TRAIL

PRAIRIE CREEK ROAD

OBRIEN ROAD

STAGE RD

WESTBROOK ROAD

JORDAN LAKE RD

SUNFIELD RD

WEST RIVERSIDE DR

S BRIDGE STREET

PECK LAKE ROAD

NASH HWY

M-21

WHITES BRIDGE RD

GRAND RIVER AVENUE

NICKLE PLATE RD

HASTINGS RD

BUTTON RD

CHARLES ROAD

NORTH BRIDGE ST

M-21

SANDERS ROAD

MORRISON LAKE RD

I-96 EB

I-96 WB

PEAKE RD

STOUDT RD

SHUMAN ROAD

I-96 WB

M-21

M-66 SB

I-96 EB

I-96 WB

I-96 WB

VAN VLECK ROAD

CAMPBELL ROAD

M-66

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