County profile · official public datasets

Custer County, SD

95 public highway bridges tracked in the FHWA National Bridge Inventory: 46.3% rated Good, 48.4% Fair, 5.3% Poor.

95
Public bridges: 46.3%
Good condition: 5.3%
Poor condition

The verdict

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

Custer County posts a top-quartile lowest Poor-condition share among rated counties in the state across rated county bridge inventory.

Top 14%
lowest Poor share in state: 5.3%
Poor-condition share: 95
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.

Custer County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Custer County ranks #9 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5.3%). Custer County, South Dakota contains 95 public highway bridges. Roughly 46.3% are rated “Good,” 48.4% “Fair,” and 5.3% “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 Custer County

Good condition

46.3%

44 of 95 rated 7-9

Fair condition

48.4%

46 of 95 rated 5-6

Poor condition

5.3%

5 of 95 rated 4 or below

In-state Poor-share rank

#9 of 66

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

Condition distribution

Share of 95 NBI-tracked bridges by lowest applicable component rating.

Good

46.3% (44)

Fair

48.4% (46)

Poor

5.3% (5)

Custer County's Poor-condition bridges carry 1,313 vehicle crossings a day

That is 1.2% of the county's reported daily bridge traffic on 5.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 263 crossings a day against 981 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 94 of 95 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

51.6% of Custer County's bridges have passed the 50-year mark

49 of the 95 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 46.3% 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 76.2% of the county's Poor-condition bridge traffic

STATE PARK RD over CENTER LAKE INLET, built 1950, carries 1,000 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 5-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 1,313 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

2
1930s

1
1940s

2
1950s

23
1960s

9
1970s

13
1980s

16
1990s

11
2000s

11
2010s

5
2020s

2

What this shows Construction peaked in the 1950s, when 23 of the county's bridges still in the inventory were built, which is 24.2% of those with a recorded year. That cohort is now 65 to 74 years old in the 2024 inventory. Its average build year (1977) matches the South Dakota average (1975).

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

The 5 South Dakota counties nearest Custer County in number of bridges, with their condition splits. Its 5.3% Poor share is the 1st-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 Custer County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Yankton County	99	41.4%	43.4%	15.2%	1983
McCook County	98	44.9%	44.9%	10.2%	1977
Custer County (this page)	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
Jackson County	89	29.2%	55.1%	15.7%	1969

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

Similar inventory size

Nearest county inventories outside SD (95 bridges here).

Pike County, AR · 95 bridges
Camden County, GA · 95 bridges
Liberty County, GA · 95 bridges
Fulton County, KY · 95 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 95 Good 44 Fair 46 Poor 5

All bridges (95)

Sort:

Custer County Bridge Snapshot

Condition distribution

Custer County's Poor-condition bridges carry 1,313 vehicle crossings a day

51.6% of Custer County's bridges have passed the 50-year mark

One structure carries 76.2% of the county's Poor-condition bridge traffic

How Custer 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 (95)

STATE PARK RD

S 11TH STREET

STATE PARK RD

STATE PARK RD

SD ROUTE 87

STATE PARK RD

BISON LANE

SD087

STATE PARK ROAD

E FRENCH CK ROAD

SPRING CK CUTOFF

SD ROUTE 87

UPPER FRENCH CK RD

UPPER FRENCH CK RD

RIVERSIDE ROAD

US016A

SD040

S FAIRBURN ROAD

SD ROUTE 87

HASSELSTROM PLACE

STATE PARK RD

US016

SD079N

US016A

US016A

SD040

SD040

SD089

SD089

SD079

SD079

SD040

US016A

STATE PARK RD

SD079S

US016A

US016

SD079S

SD079N

US016

US016

US016A

IRR SD040

SD036

SD079

US016A

FDR 345

HAZELRODT CG+SH

US016A

OLD SAWMILL ROAD

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