County profile · official public datasets

Yankton County, SD

99 public highway bridges tracked in the FHWA National Bridge Inventory: 41.4% rated Good, 43.4% Fair, 15.2% Poor.

99
Public bridges: 41.4%
Good condition: 15.2%
Poor condition

The verdict

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

Yankton County pairs a better-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 50%
lowest Poor share in state: 15.2%
Poor-condition share: 99
public highway bridges: 1983
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.

Yankton County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Yankton County ranks #33 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 15.2%). Yankton County, South Dakota contains 99 public highway bridges. Roughly 41.4% are rated “Good,” 43.4% “Fair,” and 15.2% “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 Yankton County

Good condition

41.4%

41 of 99 rated 7-9

Fair condition

43.4%

43 of 99 rated 5-6

Poor condition

15.2%

15 of 99 rated 4 or below

In-state Poor-share rank

#33 of 66

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

Condition distribution

Share of 99 NBI-tracked bridges by lowest applicable component rating.

Good

41.4% (41)

Fair

43.4% (43)

Poor

15.2% (15)

Yankton County's Poor-condition bridges carry 5,787 vehicle crossings a day

That is 5.4% of the county's reported daily bridge traffic on 15.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 386 crossings a day against 1,133 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 99 of 99 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

36.4% of Yankton County's bridges have passed the 50-year mark

36 of the 99 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 41.4% 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 68.8% of the county's Poor-condition bridge traffic

W 23RD STREET over MARNE CREEK, built 1976, carries 3,980 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 15-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 5,787 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1930s

6
1940s

12
1950s

11
1960s

3
1970s

9
1980s

13
1990s

13
2000s

11
2010s

11
2020s

10

What this shows Construction peaked in the 1980s, when 13 of the county's bridges still in the inventory were built, which is 13.1% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1983, 8 years newer than the South Dakota average of 1975.

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

The 5 South Dakota counties nearest Yankton County in number of bridges, with their condition splits. Its 15.2% Poor share is the 3rd-lowest of these 6. Its average build year of 1983 against a peer-group mean of 1977 is 6 years newer.

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

Bridge inventory size and condition shares for Yankton 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 (this page)	99	41.4%	43.4%	15.2%	1983
McCook County	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 Yankton 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 Yankton County, both outside South Dakota so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside SD (99 bridges here).

Washington County, FL · 99 bridges
Crisp County, GA · 99 bridges
Harris County, GA · 99 bridges
Newton County, GA · 99 bridges

Similar average build year

Nearest mean year-built outside SD (1983 here).

Dallas County, TX · avg 1983 · 3,230 bridges
Bexar County, TX · avg 1983 · 2,342 bridges
Sedgwick County, KS · avg 1983 · 1,333 bridges
Will County, IL · avg 1983 · 649 bridges

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

All 99 Good 41 Fair 43 Poor 15

Good-condition bridges (41)

Sort:

Yankton County Bridge Snapshot

Condition distribution

Yankton County's Poor-condition bridges carry 5,787 vehicle crossings a day

36.4% of Yankton County's bridges have passed the 50-year mark

One structure carries 68.8% of the county's Poor-condition bridge traffic

How Yankton 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 (41)

GREEN STREET

W 21ST STREET

30650 448 Ave.

44930 305 ST

45060 300TH St

30010 451 Ave

29980 NE Jim River

44950 292 ST

30690 451 Ave

29710 445th Avenue

30680 435th Avenue

29260 448 Ave

44890 294 St

45080 303 ST

DOUGLAS AVENUE

SD050 E

44780 301st Street

43780 Beaver Lake

WALNUT STREET

BURLEIGH STREET

30130 448 Ave

30140 437th Avenue

43240 Stone Chruch

US081

PINE STREET

SD046

SD050

30800 438th Ave

SD052

SD046

30950 439th Ave

29540 444th Ave

SD046

SD046

SD052

30810 437th Ave

KELLEN GROSS DR

Whiting Drive

446th Ave

44970 294st

30720 451 AVE

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