County profile · official public datasets

McCook County, SD

98 public highway bridges tracked in the FHWA National Bridge Inventory: 44.9% rated Good, 44.9% Fair, 10.2% Poor.

98
Public bridges: 44.9%
Good condition: 10.2%
Poor condition

The verdict

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

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

Top 33%
lowest Poor share in state: 10.2%
Poor-condition share: 98
public highway bridges: 1977
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.

McCook County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, McCook County ranks #22 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 10.2%). McCook County, South Dakota contains 98 public highway bridges. Roughly 44.9% are rated “Good,” 44.9% “Fair,” and 10.2% “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

Public highway bridges in McCook County

Good condition

44.9%

44 of 98 rated 7-9

Fair condition

44.9%

44 of 98 rated 5-6

Poor condition

10.2%

10 of 98 rated 4 or below

In-state Poor-share rank

#22 of 66

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

Condition distribution

Share of 98 NBI-tracked bridges by lowest applicable component rating.

Good

44.9% (44)

Fair

44.9% (44)

Poor

10.2% (10)

McCook County's Poor-condition bridges carry 911 vehicle crossings a day

That is 1% of the county's reported daily bridge traffic on 10.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 91 crossings a day against 1,769 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 98 of 98 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

45.9% of McCook County's bridges have passed the 50-year mark

45 of the 98 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 44.9% 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 36% of the county's Poor-condition bridge traffic

445 AVE (FAS 6355) over I090, built 1964, carries 328 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 911 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

4
1930s

8
1940s

5
1950s

8
1960s

15
1970s

11
1980s

11
1990s

8
2000s

10
2010s

8
2020s

9

What this shows Construction peaked in the 1960s, when 15 of the county's bridges still in the inventory were built, which is 15.3% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1977) matches the South Dakota average (1975).

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

The 5 South Dakota counties nearest McCook County in number of bridges, with their condition splits. Its 10.2% Poor share is the 2nd-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1978 is in line with the group.

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

Bridge inventory size and condition shares for McCook County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Charles Mix County	103	38.8%	37.9%	23.3%	1971
Yankton County	99	41.4%	43.4%	15.2%	1983
McCook County (this page)	98	44.9%	44.9%	10.2%	1977
Custer County	95	46.3%	48.4%	5.3%	1977
Clay County	94	58.5%	25.5%	16%	1985
Tripp County	90	27.8%	44.4%	27.8%	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 McCook 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 McCook County, both outside South Dakota so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside SD (98 bridges here).

Boone County, AR · 98 bridges
Van Buren County, AR · 98 bridges
Dougherty County, GA · 98 bridges
Butler County, KY · 98 bridges

Similar average build year

Nearest mean year-built outside SD (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

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

All 98 Good 44 Fair 44 Poor 10

All bridges (98)

Sort:

McCook County Bridge Snapshot

Condition distribution

McCook County's Poor-condition bridges carry 911 vehicle crossings a day

45.9% of McCook County's bridges have passed the 50-year mark

One structure carries 36% of the county's Poor-condition bridge traffic

How McCook 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

All bridges (98)

247th Street

432nd Avenue

438th Avenue

I090 E

258th Street

245th Street

261st Street

450th Avenue

245th Street

262nd Street

I090 W

451st Avenue

266th Street

247th Street

SD038

248th Street

I090 W

I090 E

I090 E

I090 W

248th Street

I090 E

261st Street

SD042

I090

255th Street

SD042

263rd Street

I090 W

SD042

US081

US081

443rd Avenue

US081

266th Street

SD042

252nd Street

SD038

248th Street

448th Avenue

451st Avenue

431st Avenue

263rd Street

433rd Avenue

439th Avenue

246th Street

260th Street

445 AVE (FAS 6355)

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