County profile · official public datasets

Bon Homme County, SD

126 public highway bridges tracked in the FHWA National Bridge Inventory: 21.4% rated Good, 50.8% Fair, 27.8% Poor.

126
Public bridges: 21.4%
Good condition: 27.8%
Poor condition

The verdict

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

Bon Homme County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

58th
of 66 on Poor share: 27.8%
Poor-condition share: 126
public highway bridges: 1961
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.

Bon Homme County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Bon Homme County ranks #58 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 27.8%). Bon Homme County, South Dakota contains 126 public highway bridges. Roughly 21.4% are rated “Good,” 50.8% “Fair,” and 27.8% “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

126

Public highway bridges in Bon Homme County

Good condition

21.4%

27 of 126 rated 7-9

Fair condition

50.8%

64 of 126 rated 5-6

Poor condition

27.8%

35 of 126 rated 4 or below

In-state Poor-share rank

#58 of 66

Among South Dakota counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 126 NBI-tracked bridges by lowest applicable component rating.

Good

21.4% (27)

Fair

50.8% (64)

Poor

27.8% (35)

Bon Homme County's Poor-condition bridges carry 3,069 vehicle crossings a day

That is 7.7% of the county's reported daily bridge traffic on 27.8% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 88 crossings a day against 664 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 126 of 126 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

63.5% of Bon Homme County's bridges have passed the 50-year mark

80 of the 126 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 21.4% 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 27% of the county's Poor-condition bridge traffic

SD037 over MISSOURI RIVER, built 1996, carries 830 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 35-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 3,069 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

4
1910s

5
1920s

7
1930s

26
1940s

5
1950s

10
1960s

13
1970s

16
1980s

18
1990s

8
2000s

5
2010s

4
2020s

5

What this shows Construction peaked in the 1930s, when 26 of the county's bridges still in the inventory were built, which is 20.6% of those with a recorded year. That cohort is now 85 to 94 years old in the 2024 inventory. Its average build year is 1961, 14 years older than the South Dakota average of 1975.

How Bon Homme County compares with South Dakota's closest counties by inventory size

The 5 South Dakota counties nearest Bon Homme County in number of bridges, with their condition splits. Its 27.8% Poor share is the 5th-lowest of these 6. Its average build year of 1961 against a peer-group mean of 1973 is 12 years older.

Showing the 5 closest of 65 South Dakota counties eligible for comparison.

Bridge inventory size and condition shares for Bon Homme County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Butte County	143	30.8%	57.3%	11.9%	1976
Lawrence County	136	36%	51.5%	12.5%	1980
Hand County	126	24.6%	46%	29.4%	1961
Bon Homme County (this page)	126	21.4%	50.8%	27.8%	1961
Davison County	123	34.1%	48.8%	17.1%	1973
Lyman County	114	40.4%	50%	9.6%	1975

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 Bon Homme 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 Bon Homme County, both outside South Dakota so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside SD (126 bridges here).

Bibb County, AL · 126 bridges
Coosa County, AL · 126 bridges
Lawrence County, AR · 126 bridges
Coffee County, GA · 126 bridges

Similar average build year

Nearest mean year-built outside SD (1961 here).

Westchester County, NY · avg 1961 · 774 bridges
Tehama County, CA · avg 1961 · 450 bridges
Berkshire County, MA · avg 1961 · 450 bridges
Schuylkill County, PA · avg 1961 · 368 bridges

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

All 126 Good 27 Fair 64 Poor 35

Good-condition bridges (27)

Sort:

Bon Homme County Bridge Snapshot

Condition distribution

Bon Homme County's Poor-condition bridges carry 3,069 vehicle crossings a day

63.5% of Bon Homme County's bridges have passed the 50-year mark

One structure carries 27% of the county's Poor-condition bridge traffic

How Bon Homme County compares with South Dakota'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 (27)

40550 313th Street

40740 298th Street

30490 411th Avenue

41140 306th Street

41350 304th Street

29490 422nd Avenue

Stone House Road

31060 416th Avenue

IRR SD050

41310 295th Street

30270 425th Avenue

SD050

SD037

SD046

SD052

SD052

SD050

314th Street

29620 414th Avenue

SD052

SD037

29260 423rd Avenue

SD025

SD025

SD052

SD046

SD046

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