County profile · official public datasets

Lake County, SD

79 public highway bridges tracked in the FHWA National Bridge Inventory: 44.3% rated Good, 49.4% Fair, 6.3% Poor.

79
Public bridges: 44.3%
Good condition: 6.3%
Poor condition

The verdict

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

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

Top 20%
lowest Poor share in state: 6.3%
Poor-condition share: 79
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.

Lake County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Lake County ranks #13 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.3%). Lake County, South Dakota contains 79 public highway bridges. Roughly 44.3% are rated “Good,” 49.4% “Fair,” and 6.3% “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 Lake County

Good condition

44.3%

35 of 79 rated 7-9

Fair condition

49.4%

39 of 79 rated 5-6

Poor condition

6.3%

5 of 79 rated 4 or below

In-state Poor-share rank

#13 of 66

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

Condition distribution

Share of 79 NBI-tracked bridges by lowest applicable component rating.

Good

44.3% (35)

Fair

49.4% (39)

Poor

6.3% (5)

Lake County's Poor-condition bridges carry 1,071 vehicle crossings a day

That is 1.8% of the county's reported daily bridge traffic on 6.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 214 crossings a day against 713 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 79 of 79 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

38% of Lake County's bridges have passed the 50-year mark

30 of the 79 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 44.3% 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 54.2% of the county's Poor-condition bridge traffic

461 AVE over CK, built 1950, carries 580 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 1,071 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1930s

15
1940s

7
1950s

7
1970s

9
1980s

6
1990s

10
2000s

13
2010s

7
2020s

5

What this shows Construction peaked in the 1930s, when 15 of the county's bridges still in the inventory were built, which is 19% of those with a recorded year. That cohort is now 85 to 94 years old in the 2024 inventory. Its average build year (1977) matches the South Dakota average (1975).

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

The 5 South Dakota counties nearest Lake County in number of bridges, with their condition splits. Its 6.3% Poor share is the 1st-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1974 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 Lake County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Jackson County	89	29.2%	55.1%	15.7%	1969
Moody County	87	29.9%	46%	24.1%	1973
Fall River County	80	50%	42.5%	7.5%	1982
Lake County (this page)	79	44.3%	49.4%	6.3%	1977
Codington County	74	20.3%	63.5%	16.2%	1976
Deuel County	72	22.2%	61.1%	16.7%	1971

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

Similar inventory size

Nearest county inventories outside SD (79 bridges here).

Cleveland County, AR · 79 bridges
Woodruff County, AR · 79 bridges
Barrow County, GA · 79 bridges
Edwards County, IL · 79 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 79 Good 35 Fair 39 Poor 5

Good-condition bridges (35)

Sort:

Lake County Bridge Snapshot

Condition distribution

Lake County's Poor-condition bridges carry 1,071 vehicle crossings a day

38% of Lake County's bridges have passed the 50-year mark

One structure carries 54.2% of the county's Poor-condition bridge traffic

How Lake 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 (35)

SD019

SD019

443 AVE

462 AVE

223 ST

US081

SD019

450 AVE

233 ST

902 N OLIVE AVE

224 9TH STR NE

317 HARTH AVE

316 N LEE AVE

415 N WASHNGTN AVE

111 GRANT AVENUE

725 4TH STR SE

460 AVE

241 ST

509 CENTER STR E

SD019

226 ST

US081

111 GARFIELD AVE S

456 AVE

461 AVE

US081

464 AVE

SD034 W

241 ST

241 ST

202 NW 7TH STREET

459 AVE

224 ST

213 N LINCOLN AVE

508 NE FIRST STR

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